Applied Technology
Level 6
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2 • Applied Technology
INTRODUCTION
Hi, I’m EdWIN!
Hi! Let me introduce myself to you. I am EdWIN,
and I will be your friendly guide through this study.
Now, you may have met me before in a different course
or in an earlier level. If you have, I hope that you have
found that I am not too tough of a taskmaster. Look
for me to pop up every now and then with a tip, hint,
or maybe even a quiz question or two!
You are about to begin Applied Technology, Level 6.
If you have already completed Level 5, you know that
it wasn’t too difficult. This level will cover the basics
once again for your review. The main difference will
be that the exercises will be more difficult. The great
thing about this type of learning is that you generally
can set your own pace. Consequently, you will not have
to move on until you feel you have learned the material
to your satisfaction.
As in previous levels, we will be studying
thermodynamics, fluid dynamics, electricity, and
mechanics.
So, if you are ready, so am I. Turn the page and let’s
begin!
Applied Technology • 3
STRATEGIES
Problem-Solving Strategies
The basic components of effective problem-solving strategies are:
• Identifying the problem (“What is the goal?” and “What limits does the goal
impose?”)
• Analyzing and interpreting data (reading a gauge, interpreting a printout).
This includes identifying and disregarding nonessential data.
• Exploring and evaluating solutions (“What options are available?” and “Which
option is best, taking into account many variables, including cost, time, human
resources, materials, environment, and expertise?”)
One well-known problem-solving model is the IDEAL* model. The IDEAL model
was designed as an aid for teaching and improving problem-solving skills. The
IDEAL process includes the following steps:
I
D
E
A
=
=
=
=
L
=
Identify the problem (determine what needs to be done).
Define and represent the problem (sharpen and clarify the boundaries).
Explore alternative approaches (analyze and evaluate alternatives).
Act on a plan (determine the logical steps to be used and how to progress
through the steps).
Look at the result (determine whether or not the plan worked).
The exercises in this workbook guide learners through the IDEAL problem-solving
process.
* The IDEAL Problem Solver: A Guide for Improving Thinking, Learning, and Creativity , © 1984.
Permission for use granted by W.H. Freeman and Company/Worth Publishers, all rights reserved.
4 • Applied Technology
STRATEGIES
Problem-solving strategies are critical to any instruction aimed at improving all
levels of applied technology skills. To be an effective technological problem solver,
you need to be able to do the following:
•
•
•
•
•
•
Understand cause-effect relationships (What parts of systems affect and are
affected by other parts?)
Make comparisons (What commonalities and differences do systems have?)
Recognize probable outcomes (How will the system react to a specific action?)
Predict what should happen next (Based on what has been observed, what is
known about a specific system, and what is known about related scientific
principles, make a prediction about what will happen next.)
Judge spatial relationships (Visualize how a system operates and mentally rotate
system parts to solve problems within a given system.)
Notice what appears out of place (Observe a malfunctioning system in operation
to determine what is not working correctly.)
Course Strategies
The best way for me to help you be an effective problem solver is to give you
opportunities to develop and refine your problem-solving skills. Therefore, I will
use the following strategies:
• I will mimimize instructions so that you are encouraged to invent innovative
ways to accomplish the tasks.
• I will provide you with a variety of materials from which to choose.
• If you have questions about the exercises, reread the beginning instructions.
This strategy encourages you to figure out how to use the materials to reach
your goal.
• You have plenty of time to explore. As long as you are actively engaged, learning
is taking place. If ample time is allowed, you will be able to do more in-depth
investigation. Thinking about a problem is part of learning.
• I encourage you to share ideas with others. This strategy reflects how people
solve problems in the workplace — with input from others. Most problemsolving activities lend themselves to having you work individually, but you are
encouraged to seek others’ input.
Applied Technology • 5
BASIC PRINCIPLES
BASIC SCIENTIFIC PRINCIPLES
Applied Technology focuses on:
• Principles related to power sources – for thermal,
fluid, electrical, and mechanical systems.
• Principles related to flow – for thermal, fluid,
electrical, and mechanical systems.
• Principles related to pressure – for thermal, fluid,
electrical, and mechanical systems.
• Principles related to resistance – for thermal, fluid,
electrical, and mechanical systems.
Some basic scientific principles involved with energy
sources, flow, pressure, and resistance follow:
Bernoulli’s principle: The faster the flow of air or fluid, the lower the pressure.
Boyle’s law: For a certain amount of gas, at a constant temperature, as the pressure (P)
increases, the volume (V) of the gas decreases so that P times V is constant (k). (PV=k).
Charles’ law: For a certain amount of gas, at a constant pressure, as the absolute
temperature of the gas increases, the volume of the gas also increases. Mathematically
this is: Volume (V) divided by temperature (T) equals a constant (k). V/T=k The
temperature must be on an absolute scale that is in reference to absolute zero.
Hooke’s law: The greater the force exerted on an object, the more it will be moved. For
example, the heavier the weight hanging from a spring, the more the spring will be
stretched.
Newton’s laws of motion:
• An object will remain at rest or in uniform motion unless acted upon by an
outside force.
• When a force acts upon an object, it changes the momentum of that object,
and this change is proportional to the applied force and to the time that it acts
upon the object.
• Every action (force) is followed by an equal and opposite reaction (force).
Ohm’s law: Current is directly proportional to the voltage and inversely proportional to
the resistance.
Pascal’s law: Pressure added to a confined fluid at any point instantly appears equally at
all other points, and is always at right angles to the confining surfaces.
6 • Applied Technology
OUTLINE
LESSON 1
Thermodynamics
LESSON 2
Fluid Dynamics
LESSON 3
Electricity
LESSON 4
Mechanics
LESSON 5
Posttest
REFERENCES
Test-Taking Tips
Basic Scientific Principles
Bibliography
Answers to Pop Quiz Questions
Applied Technology • 7
LESSON 1
THERMODYNAMICS
Q
Thermodynamics is a pretty complicated sounding
word, isn’t it? It is a very complicated science. There is
a lot that can be learned about it. But for our purposes,
we are not going to try to become experts in the subject!
We do want to learn the basics of the science. If you
find yourself in an employment situation that requires
some knowledge of the subject, you will have the
confidence to apply what you have learned. The
problems at this level will be more difficult than those
at previous levels. But, don’t worry; you’ll be able to
complete them.
All matter is made up of particles that are in constant
motion. This motion manifests itself as the form of
energy called heat. The study of heat is called
thermodynamics. Now, that wasn’t so hard, was it?
There are two basic laws of thermodynamics.
Basic Laws of Thermodynamics
1. Energy cannot be created or destroyed.
2. Heat energy always flows spontaneously from
hot to cold.
Next time I play I will
wear light-colored
clothing!
8 • Applied Technology
LESSON 1
Some other generalizations that can be made about
heat include:
• Heat travels through conductors such as metal better
than it travels through insulators such as brick or
wood. For example, you know that if you stir boiling
water with a metal spoon, it will soon heat up to
the point where you cannot touch it. If you stir
boiling water with a wooden spoon, you can stir it
indefinitely without it getting too hot to touch.
• Dark-colored surfaces absorb more heat than lightcolored surfaces.
• Rough or dull surfaces absorb more heat than
smooth or shiny surfaces.
• When friction causes heat, the object that is in
constant contact gets hotter than the movable
object.
In this lesson we will be specifically concentrating
on car air-conditioning. Several scientific principles are
involved in these problems including latent heat,
evaporation, condensation, and change of state of
matter.
Let’s start by describing the basic operation of a car
air-conditioning system. I know you are going to say,
“Obviously, it is to cool the passenger compartment of
the vehicle!” Yes, I know that already. But what does it
actually do, scientifically speaking? The system takes
refrigerant from the gas phase to the liquid phase and
returns it back to a gas. Each time the refrigerant
changes state, heat is either absorbed or released.
Applied Technology • 9
LESSON 1
Refer to Diagram A. The parts of the system are
labeled and the airflow is marked with arrows so that
you can follow the entire operation from start to finish.
Following the diagram, I am going to list the major
parts of the system for you and describe their functions.
Diagram A
This diagram was provided by and used with the permission of Deere & Co.
10 • Applied Technology
LESSON 1
Compressor
This device pressurizes the refrigerant. Notice in
the drawing that the compressor contains what looks
very similar to a standard piston. Basically, that is exactly
what it is! This piston pressurizes the gas. The refrigerant
is commonly called Freon. Most of you are aware that
when the Freon gets low, the air conditioner cools less
and less. Many times this is the cause of malfunctioning
systems, and the missing Freon simply needs to be
replaced. If the compressor itself is not functioning
properly, look out! It could be that there is some type
of break in the seal or other cause. The compressor has
to be completely sealed or the gas will be forced out
through the leak, therefore causing less pressurized gas
to flow into the condenser. This can cause the
compressor to work overtime and literally “burn up”
the device. This is a major repair expense.
Compressor clutch
This device allows the compressor to turn when it
is engaged. This works the same as the clutch in a
manual shift car. When you press in the clutch pedal,
this allows you to put the car in gear or change gears.
What happens when you try to engage the transmission
without pressing in the clutch pedal? Yes, that terrible
grinding noise that makes you wince as you visualize
the teeth on the gears being ground off! Big expense!
Well, the clutch on the air-conditioning system works
this way, except that you don’t have to remember to
push in a pedal to engage your air conditioner. All you
do is flip a switch on the front panel of your car which
will engage the clutch according to the setting on the
thermostat.
Applied Technology • 11
LESSON 1
Condenser
This changes the refrigerant vapor to liquid. The
refrigerant comes in a gas form. As I stated before, the
compressor does just what it sounds like. It compresses
or pressurizes the gas refrigerant. Then, the condenser
changes the gas into a liquid in order for it to flow
through the system and cool your car.
Expansion valve
This valve reduces refrigerant pressure before it
enters the evaporator. The pressure created by the
compressor causes the gas to condense and keeps the
liquid from boiling. The reduction of pressure allows
the liquid to boil. The boiling or evaporation process
requires heat, which comes from the liquid itself,
resulting in cold vapor. The cold vapor then takes heat
from the metallic fins located on the evaporator. Once
the compressor shuts off and the rest of the liquid
evaporates, the pressure in both sides of the system
equalizes; thus, the evaporator must be able to
withstand high pressure.
Evaporator
An evaporator consists of a heat exchanger in which
the liquid refrigerant is evaporated, taking its heat from
its environment. Hot liquid enters through the
expansion valve and boils, heat is transferred from the
metallic fins to the refrigerant. A blower motor is then
used to move air across the evaporator, which disperses
cool air.
12 • Applied Technology
LESSON 1
Thermostat switch
This is the mechanism I mentioned that engages
the clutch. When you turn on your air conditioner
and set the temperature that you want, the thermostat
detects the temperature in the car. If it is warmer than
the setting, it automatically engages the clutch and starts
the cooling system. This is the same way a thermostat
works in a building’s central heat and air system. Once
it has reached the temperature you have set, it turns
off. Try this yourself by turning on your car’s airconditioning system. (Be sure to turn off the radio and
roll up your windows so that you can hear!) Then, listen
to the compressor engage and disengage as the
thermostat switch turns on and off. The fan will be
blowing all the time, but the actual cooling will shut
off and on according to the thermostat reading and
the automatic switch.
This removes moisture!
Accumulator dryer
This device removes moisture and stores extra
refrigerant.
OK, have you studied the diagram closely? Have
you identified the parts of the system that I described?
Do you understand their functions? If not, study the
diagram again and reread the descriptions. This will
help you to comprehend the basic function of the
system.
Now, let’s try an exercise.
Applied Technology • 13
LESSON 1
EXERCISE – CAR AIR CONDITIONER
Instructions: Read the following scenario and refer to the diagram of the air-conditioning
unit as you answer the following questions.
Scenario
A customer brings in a car and says that the air conditioner
is not working. Specifically, on hot days it does not get cool
enough. The customer had the car’s air-conditioning system
recharged within the last week. There is also a clicking sound
coming from under the hood. Your supervisor asks you to
diagnose the problem and suggest a solution.
Identify the problem
1.
What have you been asked to do?
a. Determine why the air conditioner is not working properly.
b. Determine why the car is overheating.
c. Determine why the air-conditioning is not working properly and
discuss it with your supervisor.
d. Fix the air-conditioning system.
e. Recharge the air-conditioning system.
Define the problem
2.
The problem in the system could be that:
a.
b.
c.
d.
e.
the blower motor on the evaporator is not working properly.
the magnetic clutch is not engaging properly.
the refrigerant level is low.
the condenser is clogged.
the fan belt is broken.
14 • Applied Technology
LESSON 1
3.
To identify the cause of the malfunction, you would NOT need to:
a.
b.
c.
d.
e.
check the coil in the magnetic clutch.
see if the filter in the accumulator dryer is clogged.
check the coolant thermostat.
inspect the temperature-sensing bulb.
check the fan belts.
Explore alternatives
4.
To isolate the problem, you would FIRST:
a.
b.
c.
d.
e.
check the magnetic clutch coil.
see if the blower motor evaporator is running.
check for a clogged expansion valve.
check for a loose accumulator dryer.
check for a refrigerant leak.
Act on a plan
5.
Below are observations made of the system. Which would indicate
an existing problem?
a.
b.
c.
d.
There is a loose belt on the compressor.
The expansion valve is not clogged.
There is no continuity in the clutch coil.
The pressure on the high side is 190 psi; the pressure on the low
side is 30 psi.
e. The fan belt is frayed.
Applied Technology • 15
LESSON 1
6.
To correct the problem, you would:
a.
b.
c.
d.
e.
add refrigerant.
change the expansion valve.
change the compressor.
replace the magnetic clutch coil.
replace the refrigerant.
Look at the result
7.
If the problem has NOT been corrected, which of the following would
you expect?
a.
b.
c.
d.
e.
The air-conditioning has plenty of refrigerant.
There will be no clicking sound under the hood.
The air-conditioning system cools the car on cool days.
The air-conditioning system cools on hot days.
The air-conditioning system needs to be recharged at this time.
IDEAL
16 • Applied Technology
LESSON 1
ANSWERS TO EXERCISE
1.
What have you been asked to do?
Answer:
2.
The problem in the system could be that:
Answer:
3.
c. check the coolant thermostat.
To isolate the problem, you would FIRST:
Answer:
5.
b. the magnetic clutch is not engaging properly.
To identify the cause of the malfunction, you would NOT need to:
Answer:
4.
c. Determine why the air-conditioning is not working properly
and discuss it with your supervisor.
a. check the magnetic clutch coil.
Below are observations made of the system. Which would indicate
an existing problem?
Answer:
c. There is no continuity in the clutch coil.
Applied Technology • 17
LESSON 1
6.
To correct the problem, you would:
Answer:
7.
d. replace the magnetic clutch coil.
If the problem has NOT been corrected, which of the following would
you expect?
Answer:
e. The air-conditioning system needs to be recharged at this
time. (Add refrigerant.)
Time to move on to fluid dynamics …
18 • Applied Technology
IDEAL
Applied Technology • 19
LESSON 2
FLUID DYNAMICS
Before we get into the specifics of this lesson, I will
repeat some basic principles that we addressed
previously. This is to refresh your memory and if you
are starting with me on this level, this will give you an
opportunity to review the basics.
Some basic scientific principles involved with energy
sources, flow, pressure, and resistance appear below:
Bernoulli’s principle: The faster the flow of air or fluid, the lower the pressure.
Boyle’s law: For a certain amount of gas, at a constant temperature, as the pressure (P)
increases, the volume (V) of the gas decreases so that P times V is constant (k). (PV=k).
Charles’ law: For a certain amount of gas, at a constant pressure, as the absolute
temperature of the gas increases, the volume of the gas also increases. Mathematically
this is: Volume (V) divided by temperature (T) equals a constant (k). V/T=k The
temperature must be on an absolute scale that is in reference to absolute zero.
Hooke’s law: The greater the force exerted on an object, the more it will be moved. For
example, the heavier the weight hanging from a spring, the more the spring will be
stretched.
Newton’s laws of motion
• An object will remain at rest or in uniform motion unless acted upon by an outside
force.
• When a force acts upon an object, it changes the momentum of that object, and
this change is proportional to the applied force and to the time that it acts upon
the object.
• Every action (force) is followed by an equal and opposite reaction (force).
Pascal’s law: Pressure added to a confined fluid at any point instantly appears equally at
all other points and is always at right angles to the containing surfaces.
20 • Applied Technology
LESSON 2
Other generalizations that can be made about fluid are:
Concerning pressure
• The amount of pressure exerted by a fluid
depends upon the height and the density of
that fluid and is independent of the shape of
the container that is holding the fluid.
#
• The deeper the fluid, the greater the pressure
it exerts.
• The denser the fluid, the greater the pressure
it exerts (salt water is denser than fresh water).
• Fluids seek equilibrium - they seek their own
level; a fluid will flow from a place of high
pressure to a place of low pressure.
• A fluid can never rise higher than its source
without an external force (a pump).
Concerning evaporation
Q
• The higher a liquid’s temperature, the faster
it will evaporate.
• The lower a liquid’s pressure, the faster the
liquid will evaporate.
• The more area of liquid that is exposed to
air, the faster the liquid will evaporate.
• The more circulation of air above a liquid,
the faster the liquid will evaporate.
Applied Technology • 21
LESSON 2
Concerning boiling point
_
• Increased pressure on a liquid raises the
liquid’s boiling point.
• Decreased pressure on a liquid lowers the
liquid’s boiling point.
OK, now that we have reviewed the basics, let’s
discuss the details of this level.
We will be concentrating on cooling systems with
tanks. The primary principles involved are flow rate of
liquids, pulley systems, and open systems. There is an
equation used to determine flow rate. Before you panic
at this thought, it is not difficult, and I know you can
do it!
Flow rate is equal to volume divided by time.
The equation looks like this: Qv = V/t.
If you remember equations from school, you know
that anytime there is a forward slash (/) between
numbers or letters, it means to divide by the second
number.
22 • Applied Technology
LESSON 2
Let’s look at an example to understand this more
clearly. If you have a quart of water (volume), and it
takes two minutes for the water to flow out of a
container (time), then you divide one quart by two
and you reach a flow rate of 1/2 quart per minute. The
formula would be written like this:
Qv = V/t or
Qv =
V
t
Substitute the numerics for the letters and write the
formula as follows:
Qv = 1/2
Then, do the math. Divide 2 into 1 to get your
answer.
Qv = 1/2 quart per minute.
The flow rate (Qv) then would be 1/2 quart per
minute.
Fluids will flow from a place of high pressure to a
place of low pressure. An electric motor or the force of
gravity can provide the high pressure area. Fluid will
flow along any path that is available to it. You see this
principle anytime it is raining and the water naturally
flows downhill. That’s because gravity will force it in
that direction. You can also see the principle of “the
path of least resistance” if you watch how the water
flows in certain directions, such as through gullies or
low areas.
Applied Technology • 23
LESSON 2
For example, if you have a gravel driveway, you can
see how your driveway always washes out in the same
places. The ruts and gullies made by the water flow
will get deeper with time.
Large pipes have low pressure while smaller pipes
have greater pressure. You may be familiar with this
concept. Why do you have small diameter pipes that
are used to send water into your home? If you had larger
pipes, your water pressure would be significantly
reduced. In contrast, the pipes that drain the water or
sewer system out of your home are very large in
diameter. Why? This is to allow easy flow when you
drain the water from your bathtub or sink. What would
happen if you had the small diameter pipes hooked to
the drain system? For one, it would take forever for
your bathtub to empty!
Net flow is equal to the input flow minus the output
flow. When fluid resistance is reduced, flow rate is
increased if the pressure is constant. Fluids are typically
non-compressible.
Now, wait a minute, you might be saying. Don’t
we use hydraulic pressure to send fluids through a
system? Yes, you would be right; but, the fluid itself is
not being compressed. It is simply being forced by
pressure to do specific work. Let’s discuss this a little
further. As you know, gas can be compressed. This is
because in a gaseous substance, the molecules are spread
out in the container. Fluid molecules are more
condensed. While the gas can be compressed to take
up a smaller space, the fluid simply has no room to be
compressed.
24 • Applied Technology
LESSON 2
Thinking Activity
Suppose you have a container that has four equal-sized holes placed vertically
in the side. If you fill the container with water, which of the streams of
water would be forced out the farthest from the container?
Remembering the principle that pressure is greater
at the lowest point, you would know that the bottom
hole would produce the stream the farthest from the
container. Look at this logically. There is a greater
distance from the bottom hole to the top of the fluid
in the container. Therefore, there is more pressure being
applied to the bottom hole. Since the greatest pressure
would flow to the lowest point, the bottom hole would
be the answer.
Applied Technology • 25
LESSON 2
Thinking Activity
Suppose you have two containers of the same size, but with different size
holes in each. What will happen when you fill the containers with water?
Which stream of water will flow the farthest from its container?
This exercise goes back to the example that I gave
you earlier of your home water system. The smallest
hole will have greater pressure. Therefore, the stream
of water will be forced farther from the container than
the container with the larger hole.
This next exercise will focus on density of fluids.
26 • Applied Technology
LESSON 2
Thinking Activity
Suppose you have two containers with holes of the same size. You fill one
with water and the other with oil. Which one will force the fluid farther
from the container, the one with the water or the one with the oil?
In general, water is more dense and therefore,
heavier than oil. The water will create more pressure
and travel a greater distance than oil.
Just for comparison sake, which one would go
farther if the container with the oil contained heavy
crude oil which exerted a greater pressure than the one
with the water?
Exactly as you thought, the opposite would happen.
The oil would be pushed farther simply because it is
under greater pressure.
Applied Technology • 27
LESSON 2
OK, now that we have looked at some diagrams
and have done some thinking exercises concerning
them, let’s try some exercises dealing with flow rate.
This is where you will need to use your formula. Do
you remember it? Flow rate is volume divided by time.
Qv = V/t. Using this formula, calculate the flow rates.
Remember that net flow rate is determined by
subtracting the output rate from the input rate.
Now, I am going to give you the answers, but don’t
peek before you try to solve these problems.
Facts
Volume flow rate = Volume displaced divided by elapsed time. Qv = V/t
Net flow rate = Input rate minus output rate
4 quarts = 1 gallon
60 minutes = 1 hour
Pop Quiz:
Define compressor.
28 • Applied Technology
LESSON 2
EXERCISE – CALCULATING FLOW RATE
Instructions: Use the facts provided to answer the following questions. Round answers to
the nearest hundredth.
1.
If 200 gallons of fluid are delivered into a reservoir in 14 minutes,
what is the flow rate?
____________________________________________________________
____________________________________________________________
2.
A hose delivers water into a fountain at a rate of 0.75 gal/min. The
water flows from this fountain to other components at a rate of 0.25
gal/min. What is the net flow into the fountain?
____________________________________________________________
____________________________________________________________
3.
A 150-gallon water tank can be filled at a flow rate of 3 gal/min. How
long will it take to fill the tank?
____________________________________________________________
____________________________________________________________
Applied Technology • 29
LESSON 2
POP QUIZ:
Name the five steps of the IDEAL problem-solving strategy.
1. ______________________________________________
2. ______________________________________________
3. ______________________________________________
4. ______________________________________________
5. ______________________________________________
30 • Applied Technology
LESSON 2
ANSWERS TO EXERCISE
1.
If 200 gallons of fluid are delivered into a reservoir in 14 minutes,
what is the flow rate?
Answer:
2.
A hose delivers water into a fountain at a rate of 0.75 gal/min. The
water flows from this fountain to other components at a rate of 0.25
gal/min. What is the net flow into the fountain?
Answer:
3.
Qv = V/t
Qv = 200 gal/14 min
Qv = 14.29 gallons per minute
Input flow = .75 gallons per minute
Output flow = .25 gallons per minute
Net flow rate = 0.75 gal/min - 0.25 gal/min
Net flow = 0.5 gallons per minute
A 150-gallon water tank can be filled at a flow rate of 3 gal/min. How
long will it take to fill the tank?
Answer:
Did this one seem more difficult? If you substitute the numbers
for the equation letters, you found that you were given the
flow rate and the volume. So, which factor was the
unknown? … the time. In this one you must turn the formula
around a bit to figure it out.
t(time) = V(volume)/Qv(flow rate)
t = 150 gal/3 gal per minute
t = 50 minutes
How did you do on those exercises? If you had
trouble, go back and review as much as you need before
proceeding to the next problem.
Applied Technology • 31
LESSON 2
EXERCISE – COOLING SYSTEM WITH TANK
Instructions: Read the following scenario and refer to the diagram as you answer the following
questions.
Scenario
At your place of employment, the cooling system has a
10-horsepower motor running a positive displacement pump
at twice the speed of the motor (see diagram). The motor uses
a 10˝ driving pulley and a 5˝ driven pulley. This system is
supplying a 32-quart cooling tank that is 3´ tall. This tank
supplies two machines. The tank is 33% full. It takes 250
minutes to finish filling the tank. Your systems operator asks
you to run a system check. You find that the flow meter
readings are accurate and you get the following resistance.
______________________________________
METER
FLOW RATE
;
@
______________________________________
A
1
______________________________________
B
.5
______________________________________
C
3
It is your responsibility to analyze the system and report to
the systems operator.
Cooling System
32 • Applied Technology
LESSON 2
Identify the problem
1.
What is your assignment?
a.
b.
c.
d.
e.
to evaluate the system
to determine whether the system is outdated
to determine whether the horsepower of the motor is correct
to repair the system
to clean the cooling tank
Define the problem
2.
What do you need to do to evaluate this system?
a. Replace the pump.
b. Clear the lines of any clogs or blockages.
c. Calculate the expected flow rate as compared to the meter
readings.
d. Calculate the wattage of the motor.
e. Determine the gear ratio between the motor and the pump.
Explore alternatives
3.
What factors could account for the discrepancy between the actual
flow rate and the meter readings?
a.
b.
c.
d.
e.
The belt on the pulley is slipping.
The cooling tank is not level.
The pump is not running properly.
There is a leak ahead of Meters A and B.
There is a leak in Machines A and/or B.
Applied Technology • 33
LESSON 2
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34 • Applied Technology
LESSON 2
Act on a plan
4.
What is the BEST thing for you to do with this information?
a. Report to the systems operator that one of the machines is
leaking.
b. Replace the motor.
c. Report to the systems operator that the system is functioning
properly.
d. Report to the systems operator the exact location of the leak in
the line.
e. Change the speed of the pump to increase the fill rate to the
cooling tank.
Look at the result
5.
After you gave the report to the systems operator, a certified repair
person sealed the leak in the cooling tank. How will you verify that
the system is operating properly?
a.
b.
c.
d.
e.
Recalculate the flow rate for the cooling tank.
Measure the motor voltage.
Recalculate the motor’s horsepower.
Verify that the lines have no blockages.
Recalculate the horsepower for the motor.
Applied Technology • 35
LESSON 2
ANSWERS TO EXERCISE
1.
What is your assignment?
Answer:
2.
What do you need to do to evaluate this system?
Answer:
3.
d. There is a leak ahead of Meters A and B.
What is the BEST thing for you to do with this information?
Answer:
5.
c. Calculate the expected flow rate as compared to the meter
readings.
What factors could account for the discrepancy between the actual
flow rate and the meter readings?
Answer:
4.
a. to evaluate the system
d. Report to the systems operator the exact location of the
leak in the line.
After you gave the report to the systems operator, a certified repair
person sealed the leak in the cooling tank. How will you verify that
the system is operating properly?
Answer:
36 • Applied Technology
a. Recalculate the flow rate for the cooling tank.
LESSON 2
Before we complete fluid dynamics, let’s consider
hydraulics. Machines that make use of pressure in a
liquid are called hydraulic machines. You probably
recognize the term from common applications such as
hydraulic brakes or hydraulic lifts.
The working mechanism in a hydraulic system
contains a set of two or more cylinders containing
pistons and connected by pipes that contain hydraulic
fluid. Force is applied to the main cylinder (often called
the master cylinder) which raises the pressure of the
fluid throughout the system. This action causes pistons
in the other cylinders (slave cylinders) to create a useful
force. The amount of force is dependent upon the
diameter of the slave cylinders and the pressure applied
(psi). Pressure may be applied by a power-driven pump
(hydraulic lift ) or a manual pump (floor jack).
If the psi is constant, the wider the slave cylinder,
the greater the force applied and the shorter the distance
moved. So, a narrow slave cylinder moves a large
distance with reduced force.
Applied Technology • 37
LESSON 2
Let’s look more closely at a hydraulic lift. This type
of lift is used in a garage when an automobile is raised
for inspection. Its force is accomplished by hydraulics
even though it contains only one piston. A compressor
pumps air into an oil reservoir increasing the pressure
of the oil. This oil reservoir acts as a master cylinder.
The piston is forced up, lifting the car, when the highpressure oil flows into the base of the cylinder. Closing
the oil valve keeps the piston extended until the vehicle
is ready to be lowered. The air valve is opened to remove
the compressed air from the oil reservoir which, in turn,
reduces the oil pressure and the piston descends.
HYDRAULIC LIFT
38 • Applied Technology
LESSON 3
ELECTRICITY
As always, before we get to our specific focus, I will
review the basics of electricity and some generalizations
that can be applied to electricity. Later in this lesson,
we will focus on a control-wiring diagram, relays, and
motors.
Those who work with electricity must become
familiar with electrical codes. The National Electric
Code (NEC) is a compilation of regulations governing
the safe installation and use of electrical wiring and
equipment for both residential and commercial use.
In addition, local codes may stipulate more rigid
requirements than the NEC. It is mandatory that all
interior and exterior electrical wiring and electrical
equipment installations adhere to both NEC and local
codes.
We will not examine electrical codes in this course,
but I wanted you to be aware of their existence. Now,
let’s review basics of electricity.
Electricity is the continuous flow of electrons or
current from one atom to another. No electron flow
will occur unless there is a pathway over which the
electrons can move. This flow is similar to a water
system, where pipes or hoses move water from storage
tanks to where it is needed. In electrical wiring, the
pathway through which electrical current flows is called
a circuit. A simple circuit consists of a power source,
conductors, load, and a device for controlling current.
Each is described.
Applied Technology • 39
LESSON 3
• In buildings, the power source could be the
electrical generating stations that pump electricity
into residential and commercial buildings. However,
other common sources of electrical power include
small generators and batteries.
• Conductors, or wiring, provide a path for the
current, so it can travel from one point to another.
• A load is a device through which electricity produces
work. For example, a lamp is a load that, when
plugged in and turned on, produces light. Other
examples of loads include heaters, electric motors,
and televisions.
• Switches (on-off switches) control when electrical
current flows through circuits. Fuses and circuit
breakers are protective devices that control current
by preventing too much current from flowing in
the circuit, which would damage equipment. When
an excessive amount of electricity passes through
them, fuses and circuit breakers “blow” to stop the
flow of electricity through the circuit.
In a circuit, resistance lowers the amount of
electrical energy available to do work. Both wires and
load affect resistance. It might be helpful to think of a
similar situation with a hose that is connected to two
sprinklers. As water passes through a hose, turns or
kinks in the pathway cause friction (which is resistance)
that results in a slower flow. In addition, when some of
the water is diverted to the first sprinkler (which is a
load), less water is available for use in the second
sprinkler.
40 • Applied Technology
LESSON 3
There are two kinds of current flow. Direct current
flows in one direction. In most cases, direct current is
provided to equipment by batteries (flashlights and
portable radios). Alternating current flows in one
direction, then reverses to the other direction.
Alternating current is provided to equipment through
electrical substations in buildings. In the United States,
common household current reverses itself 60 times per
second. This results in 120v 60 cycle AC. The
international reference for cycles is defined in hertz (one
hertz = 1 cycle per second).
Measurement of electric current
The rate at which electricity flows is called
amperage. It is measured in amperes. (A 100-watt bulb
requires a current of approximately 1 ampere to make
it light up completely.) Current flow is measured with
an ammeter. Most electrically powered equipment
indicate the amount of current needed to operate it
properly.
Measurement of electrical pressure
Pressure is applied to electrons to force them to move
through a conductor and around a circuit. This pressure
is measured in volts. The pressure, or voltage, is
available in wiring circuits all of the time — whether
or not electrical equipment is being used. Voltage is
measured with a voltmeter.
Calculation of power
The amount of power derived from an electrical
device or system is its wattage. In other words, it is the
product obtained from electrical energy; it is the power
that we put into use. For example, the electric company
sells electrical energy.
Applied Technology • 41
LESSON 3
Electrical energy or power is measured in watts and
can be calculated as follows:
Tip: Make yourself a note
to memorize this
information.
For direct-current circuits:
volts × amperes = watts
For alternating-current circuits:
volts × amperes × power factor = watts
NOTE: Power factors range from 0-1. Large equipment
(an electric heater) may have a power factor as high as
1; small equipment (a small motor) may have a power
factor as low as .25.
Ohm’s law
Ohm’s law is a simple formula used to describe the
relationship between current (flow), voltage (pressure),
and resistance of an electrical circuit. Each component
interacts to affect the operation of a circuit. In other
words, because voltage pushes current through a
resistance, a change in any of the components will result
in a change in the others. The following three equations
are Ohm’s law rearranged to solve for each of the
quantities.
Current = Voltage ÷ Resistance
amps = volts ÷ ohms
I = E/R
An increase in voltage causes an
increase in electrical current flow. An
increase in circuit resistance causes a
decrease in electrical current flow.
Voltage = Current × Resistance
volts = amps × ohms
E=I×R
An increase in current causes an
increase in voltage. An increase in
resistance causes an increase in voltage.
Resistance = Voltage ÷ Current
ohms = volts ÷ amps
R = E/I
42 • Applied Technology
LESSON 3
GENERALIZATIONS THAT CAN BE MADE ABOUT ELECTRICITY:
• The longer the wire, the greater the resistance; the thinner the wire, the greater
the resistance.
• An increase in temperature of a wire causes an increase in resistance.
• An ordinary electrical cord has two wires; one for flow of current from the
power source and the other for the return ground.
• The voltage (pressure) and current (flow of electricity) directly affect how much
power is available to do work. Less energy source or lower flow will result in
less electrical power being produced and vice versa.
• A series circuit has only one path for the flow of current. In a series circuit,
objects are placed one after another and the current flows through each of
them in succession. The current is the same throughout, however, and the
voltage is divided among the objects in the circuit.
• In a parallel circuit, there are 2 or more paths, or branches, for the flow of
current. The current will divide and flow through each of the paths
simultaneously. Every branch has the same voltage and — if the appliances are
all the same — will have the same amount of current. The total circuit resistance
is less than any one branch.
• When batteries are connected in a series, the current is the same; the total
voltage is the sum of the voltage of each battery. The terminals are connected
+, -, +, -, and so on.
• When batteries are connected in parallel, the total current is the sum of the
currents in each battery; the total voltage is the same as that of one cell. The
terminals are connected +, +, +, and -, -, -.
Applied Technology • 43
LESSON 3
Diagnostic equipment
There are many different types of test equipment
which can be used to troubleshoot electrical circuits.
The most common testers include light probes,
voltmeters, ohmmeters, ammeters, and oscilloscopes.
A handy basic tester is called a multimeter. This is a
relatively inexpensive meter that can be used to measure
resistance (ohms), voltage (AC or DC), or current
(amps). They are available with an analog or digital
readout.
To familiarize you with the use of the multimeter,
we will discuss the analog readout version. The digital
meter uses the same principles.
For the discussion, refer to Diagram B which
represents the face of a meter.
Let’s look a little closer at the meter’s operation. All
readings are taken using the test probes. The probes
are color-coded. The black probe is for the common
ground/negative connection. The red probe is for the
voltage/positive connection. The probes are inserted
in the meter.
It is imperative that the leads be in the right
receptacles. Many test readings require the correct
polarity to obtain an accurate reading. The correct
polarity is for the black probe to be placed at the more
negative point of the circuit or component being tested
and the red probe placed at the more positive point.
Testing a circuit with power on and with the test probe
polarity reversed will result in erroneous readings and
will likely damage the meter.
44 • Applied Technology
LESSON 3
It is extremely important when making the tests on
active circuits (voltage present), that the probes are held
only by the plastic insulators and that you do not
contact the metal tips. Serious electrical shock or death
could result.
The face of the meter displays several scales. The
scales include ohms, DC volts, and AC volts. The scale
used is determined by the selector switch setting.
It is important to note that while the multimeter
tester will measure current, the capacity of these meters
for reading amperage is very low. The amperage capacity
is normally in milliamps and only useful in
troubleshooting integrated and transistorized circuitry.
Power circuits, household circuits, and the large current
applications require an ammeter that has a larger
capacity. Attempting to read a high current on a
standard multimeter will damage the meter.
Diagram B
Applied Technology • 45
LESSON 3
Ohms/Resistance
Resistance, measured in ohms, is taken with the
power supply to the circuit or components turned OFF.
The first step is to place the function selector switch
in the desired position. Refer to Diagram C.
Ohms/Resistance
R×1
R×10 R×1K
Look at the scale labeled ohms and compare it to
the function selection. The needle reading at the level
of 5 on the scale with the selector on R×1 equals 5×1
or 5 ohms. The needle reading at the level of 5 with
the selector on R×10 equals 5×10 or 50 ohms. The
same reading with the selector on R×1K equals 5×1000
or 5K ohms.
Prior to making a resistance measurement, the meter
must be “zeroed.” This is accomplished by selecting the
desired meter range (R×1, etc.). The metal tips of the
probes are pressed together which creates a direct short.
This means no resistance or “zero ohms.” While holding
the tips together, the ohms adjustment is turned until
the needle reads exactly zero ohms. Now, you are ready
to make your resistance reading.
Just a couple of more tips … for the most accurate
readings, you should select the lowest possible meter
range (R1) that does not result in the meter fully
deflecting to the highest end of the scale. If the meter
reads full deflection, move to the next higher scale and
try again. Also, you should make the “zero ohms”
adjustment each time you change scales.
46 • Applied Technology
LESSON 3
Resistance measurements are taken by placing the
meter in parallel with the measured circuit or
component.
Diagram C
Applied Technology • 47
LESSON 3
Voltage
The measurement of DC (direct current) and AC
(alternating current) voltages are very similar. Proper
negative and positive polarity are critical for DC
measurements. In some AC applications, polarity is not
important; however, it is a good rule to follow proper
polarity rules where possible.
Step one is to select the type of voltage to be read
(AC or DC) and the proper range on the function
selector. For unknown voltages, the highest range
should be selected. Locate the proper readout scale on
the meter and calculate the reading based on the range
selected. If the resulting reading fits in a lower scale,
move to that scale for a more accurate reading.
For voltage readings, the meter does not need to be
“zeroed.”
For voltage readings, the meter is placed in parallel
with the measured circuit or component. Refer to
Diagram C.
Current/Amps
Some multimeters will measure current, however,
the amperage must be very low. Following the same
steps as outlined in resistance and voltage
measurements, ensure the probes are in the proper
meter receptacles. Proper polarity is critical. Select the
current function and desired range. Always select the
highest range first and move to lower ranges as
appropriate.
48 • Applied Technology
LESSON 3
Unlike the resistance and voltage measurements,
the meter must be placed in series with the test circuit.
This means the circuit must be broken and the meter
attached so the current will flow directly through the
meter.
Series
Ladder circuits and controls
Different electrical components have different
functions. Their functions and characteristics are prime
considerations when designing circuits.
The following is a brief description of common
components used in practical applications.
Applied Technology • 49
LESSON 3
Manual switches
Manual switches are devices which allow operators
control of electrical circuits. Common types are direct
on/off switches, which can be push-button or toggle
switches. These switches remain in the position selected
until the operator changes them.
Momentary switches are switches that are activated
by an operator. When they are transferred, they open
or close a circuit depending on the switch design and
application for a short period of time. When the
operator releases the switch, it returns to its original
position (starter switch on your car).
Relays
A relay is a device used to control electrical circuits.
When current passes through a relay’s coils, a magnetic
effect is created which mechanically transfers electrical
switches. A relay consists of normally open or normally
closed transfer points. This means when no voltage is
applied to a relay, a circuit attached to the normally
closed points will be active and a circuit attached to
the normally open side will not have a complete circuit.
Conversely, when the relay is energized, the
normally closed points transfer and that circuit becomes
inactive. The normally open points transfer to a closed
position and activate the circuit they control.
50 • Applied Technology
LESSON 3
Motors
Motors are a main component in converting
electrical energy to work output. A basic motor has a
movable armature mounted on bushings or bearings.
The armature is surrounded by wire windings. As a
current passes through the motor windings, a magnetic
field is established which turns the armature. The
armature can then be connected to pulleys or gears to
provide work output.
The size and strength of the motor is determined
by design factors which include the applied voltage,
density and size of the wire windings, armature design,
etc. It is important to match the application with the
proper size motor.
Some motors have an overload contact built into the
motor. This is a safety device to prevent damage to the
motor from overheating. In an overheated condition,
the overload contact will open, removing the voltage
from the motor windings, and thus, stopping the
motor. When the motor cools, the contacts will
automatically close, allowing the motor to be started.
When overheating persists, the technician must
determine the origin of the problem.
Motors may also contain centrifugal switches. These
are switches that transfer as the armature speeds up
and are used to control both their own and other
circuits. As the motor slows down, the switches
deactivate.
Applied Technology • 51
LESSON 3
Diagram B
52 • Applied Technology
LESSON 3
With these component descriptions in mind, let’s
take a look at how they could be used in a practical
circuit. A ladder circuit is a series of circuits that depends
on conditioning by another circuit in order to step
through their function.
Refer to Diagram B. We’ll go through the design
operation a step at a time and then do some exercises.
The intent of this circuit is to run and control three
different motors in a priority sequence.
The circuit is powered by 120 volts AC at 60 cycles.
The emergency stop switches (ES1 and ES2) will shut
off power to the entire circuit when either of them is
activated. While the diagram shows them side-by-side,
in reality, they would be placed in different locations.
The stop switch (PB1) is a momentary switch
that is normally closed. Pushing the switch will
remove voltage from the control relay (CR1).
Applied Technology • 53
LESSON 3
Start switch (PB2) is a normally open momentary
switch, which is used to activate the entire circuit by
energizing CR1.
Step 1
PB2 is depressed to start the operation. Control relay (CR1) is energized as 120
volts is applied. Control relay points are transferred and points CR1-1 are closed.
PB2 is released and the switch contacts open; however, the control relay remains
energized as it is held on by the new circuit through CR1-1.
Step 2
The second circuit which drives motor M1 is activated by the results of Step 1.
Energizing the control relay closed relay points CR1-2. A second set of contacts
on PB-2 closes the circuit to M1, applying 120 volts. As M1 begins to turn, the
centrifugal switch contacts transfer. When PB2 is released, M1 continues to run
as it has a new hold circuit through M1-1 and CR1-2. Circuit 1 is activated.
Step 3
When motor M1 started, the centrifugal switch mechanism was activated. This
closed motor contact points M1-2. The closing of M1-2 applies 120 volts to
motor M2, and it begins to turn. Circuit three is activated.
Step 4
When motor M2 reaches speed, the centrifugal switch in M2 was activated. This
closes motor contact points M2-1. The closing of M2-1 completes the circuit to
apply 120 volts to M3. Circuit 4 is activated.
Summary
Motor M3 cannot run unless motor M2 is operating. Motor M2 cannot run
unless motor M1 is operating. In order for M1 to run, start PB2 must be depressed
and the control relay CR1 energized.
Pushing PB1 will stop the entire operation by removing voltage from the control
relay and M1.
54 • Applied Technology
LESSON 3
EXERCISE – LADDER DIAGRAM CONTROLS
Instructions: Consider the proposed problems and answer the related questions while
continuing to refer to Diagram B.
1.
Pushing PB2 energizes the control relay and starts M1. However,
when PB2 is released, the control relay is de-energized and M1 stops.
What is the likely problem?
____________________________________________________________
2.
M3 will not start. What is the likely problem?
____________________________________________________________
3.
On pushing start, nothing happens. While PB2 is depressed, the
voltage reading between test point 4 and X2 is 120 volts. What is the
likely problem?
____________________________________________________________
4.
The system has been running fine when suddenly M2 and M3 shut
down. What is the likely problem?
____________________________________________________________
5.
Nothing is running and the system cannot be started. The voltage
reading between test point 2 and X2 is zero. What is the likely
problem?
____________________________________________________________
Applied Technology • 55
LESSON 3
ANSWERS TO EXERCISE
1.
Pushing PB2 energizes the control relay and starts M1. However,
when PB2 is released, the control relay is de-energized and M1 stops.
What is the likely problem?
Answer:
2.
M3 will not start. What is the likely problem?
Answer:
3.
open coil wire on control relay
The entire applied voltage will be read across an open circuit.
The system has been running fine when suddenly M2 and M3 shut
down. What is the likely problem?
Answer:
5.
faulty motor contact at M2-1
It is possible there is an overload contact at M3: however, it is
unlikely as motor has not been running and is cool.
On pushing start, nothing happens. While PB2 is depressed, the
voltage reading between test point 4 and X2 is 120 volts. What is the
likely problem?
Answer:
4.
faulty contacts at CR1-1
No hold circuit is provided for the control relay.
M2 overload contact and/or M1-2 motor contact
Nothing is running and the system cannot be started. The voltage
reading between test point 2 and X2 is zero. What is the likely
problem?
Answer:
56 • Applied Technology
emergency stop switch activated or defective
LESSON 4
MECHANICS
Congratulations, you’ve almost made it! This is our
last lesson in Level 6 of Applied Technology. I hope you
have progressed steadily through this level, and through
the entire course if you have been with me from the
beginning.
As usual, I will repeat the basic concepts of machines
just in case you need the review or if you have just
started your study on this level. Look over them and
refresh your memory regarding these principles before
you start the rest of the lesson.
Hooke’s law
The greater the force exerted on an object, the
more it will be moved.
Do you think Newton had
a clue how many golfers
would practice his laws?
For example, the heavier the weight hanging from
a spring, the more the spring will be stretched.
Newton’s laws of motion
An object will remain at rest or in uniform
motion unless acted upon by an outside force.
When a force acts upon an object, it changes
the momentum of that object. This change is
proportional to the applied force and to the
time that it acts upon the object.
Every action is followed by an equal and
opposite reaction.
Applied Technology • 57
LESSON 4
Other generalizations about mechanics:
A machine is something that does work.
Work is done when a force causes an object to move.
Simple machines (gears, pulleys, inclined planes,
levers, wheel and axle) make up compound (or
complex) machines.
Compound machines include a bicycle, a rod and
reel, a typewriter, a can opener, scissors, a hand drill, a
car, a weight machine, and a treadmill.
Gears
• The force that is applied to a driver gear is transferred to a driven gear.
• When two gears of different sizes are meshed
together, the smaller gear turns faster (more
rotations per minute) than the larger gear.
• Gears that are meshed together move in opposite
directions.
• The direction and speed of the driver gear
determines the speed and direction of gears that
are meshed with it.
58 • Applied Technology
LESSON 4
Pulleys
• A pulley is a wheel with a rope, belt, or chain around
it.
• Pulleys change the direction of movement and make
work easier.
• Fixed pulleys change the direction that something
is moved; they do not make work easier.
• Movable pulleys change the direction that
something is moved and make work easier.
• The more pulleys in the system, the easier it is to
do work (pull or lift an object).
• The more pulleys involved in a system, a greater
distance must be pulled, but the easier it is to do
work.
• The thinner the windlass (winch), the easier it is to
turn.
• In two different sets of pulleys, if the wheels are
connected by a shaft and the two wheels on one
pulley are the same size as the two wheels on the
other pulley, they will both turn at the same speed.
• Common pulley applications include crankshafts,
sailboats, and window blinds.
Inclined Planes
• An inclined plane is a slanted surface that is used to
raise or lower heavy objects from one position to
another.
• Inclined planes help reduce the amount of force
needed to do a given amount of work, but require
greater distance.
• The steeper the plane, the more difficult the work.
• Wedges* are two back-to-back inclined planes.
• Common applications of inclined planes include a
screw*, a bolt, a drill bit, a clamp, a car jack, and a
screw-on bottle top.
*Some textbooks refer to the wedge and screw as basic simple machines.
Applied Technology • 59
LESSON 4
Levers
• A lever is a bar or rod that is free to move or turn
on a fulcrum.
• A lever multiplies force, but some distance must be
given up.
• The shorter the effort arm, the less force is attained
and the greater distance is attained.
• The longer the effort arm, the more force is attained
and the less distance is attained.
• Examples of levers include scissors, a broom, a claw
hammer, a nutcracker, a mop, tongs, a crowbar, a
can opener, tweezers, a baseball bat, boat oars, and
a car jack handle.
Wheel and Axle
• A wheel and axle is like a spinning lever (an ice
cream machine crank).
• The center of the axle is the fulcrum.
• The wheel is larger than the axle; for one rotation,
a point on the edge of the wheel travels a greater
distance than a point on the axle. While the work
done by the axle and the wheel are the same, the
greater distance traveled of the point on the edge of
the wheel yields a smaller force at the edge of the
wheel versus the edge of the axle.
• Common wheel and axle applications include a
screwdriver, roller skates, a water-faucet handle, a
bicycle pedal, a can opener, and a car steering wheel.
Spatial Visualization
Spatial visualization involves the ability to
manipulate and mentally rotate two-dimensional and
three-dimensional objects. Spatial orientation involves
the ability to perceive the elements in a pattern, to
compare patterns, and to grasp changing orientation
in space.
60 • Applied Technology
LESSON 4
These types of spatial skills are highly correlated
with the success you can achieve in a number of
technical and professional employment situations.
Spatial orientation is necessary to have a good sense of
direction for tasks such as reading schematics, diagrams,
or even maps.
Let’s review a learning activity. Have you used
spatial visualization to accomplish a task? I’ll bet you
have!
Thinking Activity
<
Suppose you are moving and you have to load a refrigerator, an empty
dresser, and various boxes of miscellaneous items into a truck. Which would
you load first? Why?
Here’s what I would do. Compare your answer with
mine.
I would load the refrigerator first, placing it against
the wall near the cab of the truck. This places the weight
forward of the rear axle. By placing the refrigerator in
the center of the wall, rather than against a left or right
wall, you will distribute the weight. This will prevent
the vehicle from being difficult to handle.
Then, I would load the next biggest item, the empty
dresser, in one of the back corners. I would fit the boxes
and other miscellaneous items around the larger ones
for the best stability and least movement. Heavier boxes
should go on the opposite side of the dresser as much
as possible in order to balance the weight of the dresser.
Applied Technology • 61
LESSON 4
Do you see why visually planning how to load the
truck is better than haphazardly placing items without
considering balancing the weight? You would if you
had to drive the truck on a curvy road!
OK, now that we have reviewed the basics, let’s dive
into this lesson. We will be focusing on conveyor belts
with pulleys. The principle involved will include
friction, power train (pulley system), and force
transformers.
This type of information can be used in a wide
variety of work situations and applications. Some of
them include vibration analysis, manufacturing, drive
trains, maintenance, and frictional wearing of
machinery.
62 • Applied Technology
LESSON 4
Effects of friction and heat
You already know about the principle of friction.
When two or more objects are rubbed together, they
produce friction, which produces heat. Sometimes this
can be a wanted reaction, such as when starting a fire
using friction as your heat source. Also, friction is
produced when you apply brakes on your car. The
friction or pressure on the brake shoes or pads causes
the car to come to a stop. It also produces a great deal
of heat. If you have ever driven down a steep incline
or a steep mountain road, you may have noticed that
the brakes began to smell “hot” after a while. Even
though the brakes are still working, the heat produced
by the friction begins to actually burn away the pads,
causing the smell. This is not a very good condition,
and depending on how hot the brakes are getting, you
may have to pull over and let them cool down before
continuing. This will, of course, prolong the life of your
brake pads or shoes, as burning away the surface of the
pads will cause excessive wear, which will eventually
require a quicker replacement.
Friction is often an unwanted occurrence. That is
why we keep oil in our car engines and many other
machine parts. Lubrication reduces friction; it allows
smooth movement of parts and prevents heat and
burning of the part. You know what happens when
you fail to keep your car engine’s oil sump full! The
heat produced by the constant movement of parts in
the engine will literally burn up your engine. The heat
also breaks down the oil after a certain amount of time,
and the oil must be replaced. If you do not do this
periodically, you will ruin the engine.
Applied Technology • 63
LESSON 4
You can prove this principle to yourself very easily.
If you take sandpaper and sand a board, you will see
the dust particles literally fly from the board. If you
use an emery board or a nail file on your nails, you see
immediate results with smoother nails. Also, you can
prove the heat concept by sanding the board very swiftly
using moderate pressure, and you immediately touch
the board after sanding. You will notice that it is warm
to the touch.
Applications regarding this principle are common
in everyday life.
Pulley Drive Systems: Pulley systems are commonly
used. The basic idea of a pulley system is to be able to
move, lift, or do more work than a human’s strength
would be able to do. The larger diameter pulley would
rotate less often than the smaller diameter pulley. You
can understand this concept by simply studying two
different size bicycles. The bike with the larger wheels
will turn less times to move the same distance as the
bike with the smaller wheels. If you want to prove this
to yourself, you can observe two different size bicycles.
Mark each bike wheel with a chalk mark. Mark a spot
on the pavement at the back of the wheel. Then roll
the bike forward 360 degrees. Then, mark the pavement
at the end distance. Do the same with the smaller bike.
You will see that the distance traveled was less with the
smaller bike. That’s why you have to pedal twice as fast
as the guy who’s on the bigger bike in order to keep up
with him! The guy who is pedaling twice as fast should
have to exert only half the force. Since work equals
force times distance, the amount of work of both guys
should be the same.
64 • Applied Technology
LESSON 4
Look at the following diagrams. Determine which
wheels will rotate more.
Applied Technology • 65
LESSON 4
66 • Applied Technology
LESSON 3
Bearings: Ball bearings are used to reduce friction
and heat in machine parts. A common example of this
concept is a conveyor belt. The belt sits on top of
bearings or rollers, and the belt moves smoothly.
Imagine how inefficient the conveyor would be if there
were no bearings or rollers under it. It would be literally
pulled by some force to make it move. This would cause
excessive pressure on the belt and excessive heat on the
main rollers on which the belt was attached. More force
would have to be used to pull the belt; whereas, with
the belt placed on bearings or rollers, it would move
more smoothly and less force would be exerted to move
it.
Thinking Activity
<
Here’s a thinking question for you to consider. Why can’t you just use some
type of oil or other lubricant under the belt to effect smooth movement
and use less force to move it?
Conveyor belts by necessity must be free of oil
simply because it is too messy for that purpose. Boxes,
parts, or other items cannot be subjected to contact
with any lubricant or substance that would create a
wet, dirty, or messy part. Imagine being the person who
is unloading boxes from a conveyor belt for loading
onto a delivery truck. That would be great wouldn’t it,
when the boxes were covered in oil? I don’t think that
would be tolerated well at all! Therefore, the bearings
or roller application is used instead.
Let’s think about a problem concerning pulleys and
conveyor belts.
Applied Technology • 67
LESSON 4
EXERCISE – CONVEYOR BELT WITH PULLEYS
Instructions: Read the following scenario and refer to the diagram as you answer the following
questions.
Scenario
You are a member of the maintenance department of a small
manufacturing facility.Your responsibility is to perform routine
maintenance, troubleshoot, and solve equipment malfunctions. The plant contains many conveyor-belt systems
of various types. The conveyors transport loads of 50-100 lb
loads. One particular conveyor-belt system requires an
abnormally high amount of repair as compared to other
similar systems. The problem conveyor belt, as shown in the
diagram, is powered by an electric motor. (For clarity, the
protective housings are not shown.)
Maintenance personnel report a number of chronic
symptoms. It has been observed that the conveyor belt
changes speed sporadically and often moves sluggishly. At
times, there is an odor of burnt rubber. The drive belt requires
replacement more frequently than normal. In addition, the
noise level is abnormally high. As the motor speed increases,
the noise level increases and the motor overheats.
Your job is to repair the conveyor-belt system so that it meets
normal operating conditions. Refer to the following diagram
as needed.
68 • Applied Technology
LESSON 4
Conveyor feed system
Conveyor belt
Electric motor
1,760 rpm
10 hp
240 v AC
Belt roller
Structural support
Identify the Problem
1.
What is your assigned task?
a.
b.
c.
d.
e.
to lubricate the bearings
to reduce the conveyor-belt load
to increase the production rate
to find the causes of sluggish operation
to check the motor speed in rpm
Define the Problem
2.
What should you base your investigation upon?
a.
b.
c.
d.
e.
the loads
symptoms reported by the maintenance personnel
the production rate
the motor speed
the cost of the repairs
Applied Technology • 69
LESSON 4
Examine Alternatives
3.
What subsystem is most likely responsible for the symptoms
observed?
a. electric motor
b. mechanical drive system between the electric motor and the belt
roller
c. conveyor belt and rollers
d. conveyor feed system
e. structural support system of the conveyor belt
4.
What is the most probable cause of the system’s high maintenance?
a.
b.
c.
d.
e.
The motor speed is too low.
The belt tension is improper.
The material load is too great.
A drive pulley on the motor is misaligned.
The voltage to the motor is low.
Act on a Plan
5.
Considering the reported symptoms, which procedure would you
perform FIRST?
a.
b.
c.
d.
e.
Check the power voltage to the motor.
Replace the drive belt.
Lubricate the bearings.
Replace the belt rollers.
Check the drive-belt’s alignment.
70 • Applied Technology
LESSON 4
Look at the Result
6.
You inspected the drive-belt system and found it to be misaligned.
You realigned the drive-belt system. After realigning the drive belt
and pulleys, what would you do to see if the problem is eliminated?
a.
b.
c.
d.
e.
Restart the conveyor belt.
Check the conveyor belt tension.
Check the motor speed.
Restart the conveyor belt and monitor the system’s operation.
Estimate the production rate.
IDEAL
Applied Technology • 71
LESSON 4
ANSWERS TO EXERCISE
1.
What is your assigned task?
Answer:
2.
What should you base your investigation upon?
Answer:
3.
b. mechanical drive system between the electric motor and
the belt roller
What is the most probable cause of the system’s high maintenance?
Answer:
5.
b. symptoms reported by the maintenance personnel
What subsystem is most likely responsible for the symptoms
observed?
Answer:
4.
d. to find the causes of sluggish operation
d. A drive pulley on the motor is misaligned.
Considering the reported symptoms, which procedure would you
perform FIRST?
Answer:
72 • Applied Technology
e. Check the drive-belt’s alignment.
LESSON 4
6.
You inspected the drive-belt system and found it to be misaligned.
You realigned the drive-belt system. After realigning the drive belt
and pulleys, what would you do to see if the problem is eliminated?
Answer:
d. Restart the conveyor belt and monitor the system’s
operation.
Are you ready to move on?
Applied Technology • 73
LESSON 5
Well, that’s it. How did you do? If you had trouble
or did not understand some of the concepts in this
level, go back and review all that you need. Then take
the Posttest. I will provide the answers, as usual, at the
end. But, don’t peek beforehand! That won’t help you!
Good luck.
No peeking!
74 • Applied Technology
POSTTEST
EXERCISE – POSTTEST
Instructions: Answer the following questions about the principles of applied technology.
1.
All matter is made up of particles that are in constant motion. This
motion manifests itself as the form of energy called ____________.
2.
The study of heat is called _________________________.
3.
Energy can be created but not destroyed. True or False?
4.
Heat requires a force to be applied to enable it to flow from hot to
cold. True or False?
5.
Which object will reflect heat better, a light-colored object or a darkcolored object? __________________________
6.
Describe the basic operation of a car’s air-conditioning system.
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________
7.
What is the function of the compressor?
_____________________________________________________________
_____________________________________________________________
Applied Technology • 75
POSTTEST
8.
The part that changes the refrigerant vapor into a liquid is the
___________________________.
9.
The device that engages and makes the compressor run is the
____________________________________.
10. Flow rate is equal to ____________________ divided by time.
11. Solve for flow rate: One gallon of water takes four minutes to flow
from a container.
12. Fluids will flow from a place of high pressure to low pressure. True
or False?
13. Fluid will flow along any path that is available to it. This is also
referred to as ____________________________________________.
14. Which container will empty faster if holes are placed at the same
height in the containers; one has a large hole and one has a small
hole?
_____________________________________________________________
15. From which container will the stream of water be pushed the
farthest?
_____________________________________________________________
76 • Applied Technology
POSTTEST
16. If the holes are the same size, which container will empty faster if
one is filled with oil and one is filled with water?
_____________________________________________________________
17. Explain your answer to the previous question.
_____________________________________________________________
_____________________________________________________________
_____________________________________________________________
18. _____________________ law states that the greater the force exerted
on an object the more it will be moved.
19. Give two examples where friction is a necessary force.
_____________________________________________________________
_____________________________________________________________
20. Friction always produces ___________________________.
21. What are two methods that can be used to prevent unwanted friction?
_____________________________________________________________
_____________________________________________________________
Applied Technology • 77
POSTTEST
22. A larger diameter pulley will rotate (less, more) often than a smaller
one. (Circle the correct answer.)
23. If you have two bicycles with different size wheels, which one will
travel the least distance in one revolution?
_____________________________________________________________
24. Why are ball bearings used to reduce friction in some applications?
_____________________________________________________________
_____________________________________________________________
25. Why should you replace the oil in your car engine periodically?
_____________________________________________________________
_____________________________________________________________
26. Bernoulli’s principle states that the faster the flow of air or fluid, the
(lower, higher) the pressure. (Circle the correct word.)
27. All matter is made up of particles that are in _____________________.
28. Newton’s third law of motion states that for every action there is
______________________________.
78 • Applied Technology
POSTTEST
29. The study of heat is called:
a. hydraulics
b. thermodynamics
c. pneumatics
30. Name two devices that are components of a heating and cooling
system.
____________________________________________________________
____________________________________________________________
31. What is the purpose of a condenser?
____________________________________________________________
32. The device used to engage the compressor in a car air-conditioning
system is called a _________________________.
33. What is the purpose of the blower motor?
____________________________________________________________
____________________________________________________________
34. What is the purpose of the thermostat?
____________________________________________________________
____________________________________________________________
Applied Technology • 79
POSTTEST
35. If the pressure in a hydraulic lift remains constant, would a wide
slave cylinder or a narrow slave cylinder move farther?
____________________________________________________________
36. Besides protecting from electrical overload, what is another purpose
of fuses and circuit breakers?
____________________________________________________________
____________________________________________________________
37. What is the purpose of vents in a piece of equipment?
____________________________________________________________
____________________________________________________________
38. What does the fan in a computer do?
____________________________________________________________
____________________________________________________________
39. A fan moves the air around the room, but it does not actually cool
the air. True or False?
40. Heat always stays near the floor while cooler air rises to the ceiling.
True or False?
41. Another term for pneumatic pressure is _______________.
80 • Applied Technology
POSTTEST
42. Water or oil pressure is called _________________.
43. What benefit does compressed air provide?
____________________________________________________________
____________________________________________________________
44. A water flow system has ________________________ to control and
direct the flow of water.
45. In a home water system, when you open all the faucets, what will
happen?
____________________________________________________________
____________________________________________________________
____________________________________________________________
46. Current that flows in only one direction is called:
a. alternating current
b. direct current
47. The rate at which current flows is called:
a. voltage
b. amperage
c. wattage
Applied Technology • 81
POSTTEST
48. The amount of power derived from an electrical device is:
a. voltage
b. amperage
c. wattage
49. Pressure is applied to electrons to force them through a conductive
material. This pressure is measured in:
a. volts
b. amps
c. watts
50. Name at least three simple machines.
____________________________________________________________
____________________________________________________________
____________________________________________________________
51. A ________________ machine is one that is made up of more than
one simple machine.
52. Give two examples of a compound or complex machine.
____________________________________________________________
____________________________________________________________
82 • Applied Technology
POSTTEST
53. A ______________________ is something that does work.
54. A machine that consists of two inclined planes placed back to back
is called a ____________________.
55. The center of an axle is called the:
a. lever
b. hub
c. fulcrum
56. How would you load a truck with the following items: piano, dresser,
four chairs, assorted boxes?
____________________________________________________________
____________________________________________________________
____________________________________________________________
57. Why would positioning be important in the previous question?
____________________________________________________________
____________________________________________________________
____________________________________________________________
Applied Technology • 83
POSTTEST
58. ________________ ________________ involves the ability to
mentally manipulate and rotate two- and three-dimensional
objects.
59. A window blind is an example of:
a. gear
b. inclined plane
c. pulley
60. A wood screw is an example of:
a.
b.
c.
d.
gear
lever
inclined plane
wedge
84 • Applied Technology
POSTTEST
ANSWERS TO EXERCISE
1.
All matter is made up of particles that are in constant motion. This
motion manifests itself as the form of energy called ____________.
Answer:
2.
The study of heat is called ____________________.
Answer:
3.
false
Which object will reflect heat better, a light-colored object or a darkcolored object?
Answer:
6.
false
Heat requires a force to be applied to enable it to flow from hot to
cold. True or False?
Answer:
5.
thermodynamics
Energy can be created but not destroyed. True or False?
Answer:
4.
heat
light-colored object
Describe the basic operation of a car’s air-conditioning system.
Answer:
It takes refrigerant from a gas stage to a liquid stage and
back to a gas stage.
Applied Technology • 85
POSTTEST
7.
What is the function of the compressor?
Answer:
8.
The part that changes the refrigerant vapor into a liquid is the
___________________________.
Answer:
9.
It pressurizes gas.
condenser
The device that engages and makes the compressor run is the
____________________________________.
Answer:
compressor clutch
10. Flow rate is equal to ____________________ divided by time.
Answer:
volume
11. Solve for flow rate: One gallon of water takes four minutes to flow
from a container.
Answer:
Qv = one quart per minute or 1/4 gallon per minute
12. Fluids will flow from a place of high pressure to low pressure. True
or False?
Answer:
86 • Applied Technology
true
POSTTEST
13. Fluid will flow along any path that is available to it. This is also
referred to as ____________________________________________.
Answer:
path of least resistance/gravity
14. Which container will empty faster if the holes are placed at the same
height in the containers; one with a large hole or one with a small
hole?
Answer:
the container with the larger hole
15. From which container will the stream of water be pushed the
farthest?
Answer:
the container with the smaller hole
16. If the holes are the same size, which container will empty faster if
one is filled with oil and one is filled with water?
Answer:
the container with water
17. Explain your answer to the previous question.
Answer:
Generally speaking, oil is of lesser density; therefore, it will
flow slower allowing the container with the water to empty
faster.
18. _____________________ law states that the greater the force exerted
on an object the more it will be moved.
Answer:
Hooke’s
Applied Technology • 87
POSTTEST
19. Give two examples where friction is a necessary force.
Answer:
Answers may vary.
• brakes on a car
• tires on pavement
• starting a fire
• clutch on a car
20. Friction always produces ___________________________.
Answer:
heat
21. What are two methods that can be used to prevent unwanted friction?
Answer:
Answers may vary.
• lubricant (oil)
• ball bearings
22. A larger diameter pulley will rotate (less, more) often than a smaller
one.
Answer:
less
23. If you have two bicycles with different size wheels, which one will
travel the least distance in one revolution?
Answer:
the one with the smaller wheels
24. Why are ball bearings used to reduce friction in some applications?
Answer:
88 • Applied Technology
In many situations, oil is too messy and not a practical solution.
POSTTEST
25. Why should you replace the oil in your car engine periodically?
Answer:
The heat from the friction in the engine will cause the oil to
break down, making it less efficient in keeping the engine
parts from overheating.
26. Bernoulli’s principle states that the faster the flow of air or fluid, the
(lower, higher) the pressure.
Answer:
lower
27. All matter is made up of particles that are in ________________.
Answer:
constant motion
28. Newton’s third law of motion states that for every action there is
______________________________.
Answer:
an equal and opposite reaction
29. The study of heat is called:
Answer:
b. thermodynamics
30. Name two devices that are components of a heating and cooling
system.
Answer:
Any two of the following:
compressor
shutoff valve
diffusers
filters
ductwork
blower
condenser
evaporator
thermostat
(others)
Applied Technology • 89
POSTTEST
31. What is the purpose of a condenser?
Answer:
It changes gas (pressurizes) into a liquid.
32. The device used to engage the compressor in a car air-conditioning
system is called a ___________________________.
Answer:
compressor clutch
33. What is the purpose of the blower motor?
Answer:
The blower forces the air into the ductwork.
34. What is the purpose of the thermostat?
Answer:
The thermostat senses and controls the temperature.
35. If the pressure in a hydraulic lift remains constant, would a wide
slave cylinder or a narrow slave cylinder move farther?
Answer:
narrow slave cylinder
36. Besides protecting from electrical overload, what is another purpose
of fuses and circuit breakers?
Answer:
90 • Applied Technology
They stop the electrical current when a preset temperature
on a device is exceeded, preventing overheating of the device.
This protects the individual components in the system.
POSTTEST
37. What is the purpose of vents in a piece of equipment?
Answer:
ventilation, allowing air to move so that heat will not
accumulate
38. What does the fan in a computer do?
Answer:
cools the components
39. A fan moves the air around the room, but it does not actually cool
the air. True or False?
Answer:
true
40. Heat always stays near the floor while cooler air rises to the ceiling.
True or False?
Answer:
false
41. Another word for pneumatic pressure is _______________.
Answer:
air pressure
42. Water or oil pressure is called _________________.
Answer:
hydraulic pressure
43. What benefit does compressed air provide?
Answer:
Compressed air allows a device to apply much more power
to do work.
Applied Technology • 91
POSTTEST
44. A water flow system has ________________________ to control and
direct the flow of water.
Answer:
valves
45. In a home water system, when you open all the faucets, what will
happen?
Answer:
Water pressure will be reduced at all the faucets.
46. Current that flows in only one direction is called:
Answer:
b. direct current
47. The rate at which current flows is called:
Answer:
b. amperage
48. The amount of power derived from an electrical device is:
Answer:
c. wattage
49. Pressure is applied to electrons to force them through a conductive
material. This pressure is measured in:
Answer:
92 • Applied Technology
a. volts
POSTTEST
50. Name at least three simple machines.
Answer:
Any three of the following:
wheel and axle
pulley
gear
inclined plane
lever
51. A ________________ machine is one that is made up of more than
one simple machine.
Answer:
compound or complex
52. Give two examples of a compound or complex machine.
Answers:
Any two of the following:
bicycle
car
typewriter
weight machine
scissors
can opener
treadmill
hand drill
rod and reel
(numerous others)
53. A ______________________ is something that does work.
Answer:
machine
54. A machine that consists of two inclined planes placed back to back
is called a ____________________.
Answer:
wedge
Applied Technology • 93
POSTTEST
55. The center of an axle is called the:
Answer:
c. fulcrum
56. How would you load a truck with the following items: piano, dresser,
four chairs, assorted boxes?
Answer:
Put the piano against the center of the back wall. Put the
dresser against one of the back corners. Make sure that the
heavier boxes are on the opposite side as the dresser. Put
chairs against the side walls and assorted boxes around the
other furniture.
57. Why would positioning be important in the previous question?
Answer:
The proper balance must be maintained to provide the best
equilibrium possible.
58. ________________ ________________ involves the ability to
mentally manipulate and rotate two- and three-dimensional
objects.
Answer:
Spatial visualization
59. A window blind is an example of:
Answer:
c. pulley
60. A wood screw is an example of:
Answer:
94 • Applied Technology
c. inclined plane
CALCULATING YOUR SCORE
Calculate your score counting the number of questions you answered correctly. If a
problem asked you to list several items or steps and you missed one or more, count the
question as answered incorrectly. Divide the number of your correct answers by 60.
Change the decimal answer to a percentage by moving the decimal two places to the
right.
Applied Technology • 95
SUMMARY
Congratulations on your
progress!
How well did you do on the Posttest? If you scored
90% or higher, have a reasonable chance to pass Level
6 of the ACT WorkKeys ® Applied Technolog y
assessment. Remember to use the IDEAL model when
solving problems.
I
D
=
=
E
A
L
=
=
=
Identify the problem
Define and represent the problem
boundaries
Explore alternative approaches
Act on a plan
Look at the result
Now, don’t be discouraged if you scored below 90%.
Practice the exercises in this course – you can do it.
Your enhanced work skills will pay off in the long run.
Don’t forget to practice your problem-solving skills and
read the Test-Taking Tips.
96 • Applied Technology
REFERENCE
EDWIN’S TEST–TAKING TIPS
Preparing for the test . . .
Complete appropriate levels of the WIN Instruction Solution self-study courses. Practice
the exercises until you begin to feel comfortable solving problems.
Get a good night’s rest the night before the test and eat a good breakfast on test day.
Your body (specifically your mind) works better when you take good care of it.
You should take the following items with you when you take the ACT WorkKeys®
Applied Technology assessment: (1) pencils; pens are not allowed to be used on the
test; it is a good idea to have more than one pencil since the test is timed and you do
not want to waste time sharpening a broken pencil lead; and (2) your calculator; be
sure your batteries are strong if you do not have a solar-powered calculator and that
your calculator is working properly. Pencils will be provided for those who need them.
Allow adequate time to arrive at the test site. Being in a rush or arriving late will likely
upset your concentration when you actually take the test.
About the test . . .
The test is comprised of approximately 32 multiple-choice questions. The questions
cover four areas: thermodynamics, fluid dynamics, electricity, and mechanics. Some
questions will be presented as single questions while others may be in groups of two
and refer to specific figures or scenarios. You will not be penalized for wrong answers,
so it is better to guess than leave blanks. You will have 45 minutes to complete the
test.
You will not be allowed to use scratch paper, but there is room in your assessment
booklet to make calculations in solving.
Applied Technology • 97
REFERENCE
During the test . . .
Listen to instructions carefully and read the test booklet directions. Do not hesitate
to ask the administrator questions if you do not understand what to do.
Pace yourself since this is a timed test. The administrator will let you know when you
have 5 minutes left and again when you have 1 minute remaining. Work as quickly as
possible, but be especially careful as you enter numbers into your calculator.
If a problem seems too difficult when you read it, skip over it (temporarily) and move
on to an easier problem. Be sure to put your answers in the right place. Sometimes
skipping problems can cause you to get on the wrong line, so be careful. You might
want to make a mark in the margin of the test, so that you will remember to go back
to any skipped problems.
Since this is a multiple-choice test, you have an advantage answering problems that
are giving you trouble. Try to eliminate any unreasonable answers and make an
educated guess from the answers you have left.
If the administrator indicates you have one minute remaining and you have some
unanswered questions, be sure to fill in an answer for every problem. Your guess is
better than no answer at all!
If you answer all of the test questions before time is called, use the extra time to check
your answers. It is easy to hit the wrong key on a calculator or place an answer on the
wrong line when you are nervous. Look to see that you have not accidentally omitted
any answers.
Dealing with test anxiety . . .
Being prepared is one of the best ways to reduce test anxiety. Remember to use the
five steps that we used in solving problems: identify the problem, define the problem,
explore alternatives, act on a plan, and look at the result. Identifying several ways to
solve problems and following a systematic process should increase your confidence
and reduce anxiety.
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Do not think negatively about the test. The story about the “little engine that could”
is true. You must, “think you can, think you can, think you can.” If you prepare
yourself by studying problem-solving strategies, there is no reason why you cannot be
successful.
Do not expect yourself to know how to solve every problem. Do not expect to know
immediately how to work the problems when you read them. Everyone has to read
and reread problems when they are solving problems. So, don’t get discouraged; be
persistent.
Prior to the test, close your eyes, take several deep breaths, and think of a relaxing
place or a favorite activity. Visualize this setting for a minute or two before the test is
administered.
During the test if you find yourself tense and unable to think, try the following
relaxation technique:
1.
2.
3.
4.
5.
Put your feet on the floor.
Grab under your chair with your hands. (Hope there are no surprises!)
Push down with your feet and up on your chair at the same time - hold for 5
seconds.
Relax 5 seconds (especially try to relax your neck and shoulders).
Repeat a couple of times as needed, but do not spend the entire 45 minutes of
test trying to relax!
Studying with a partner is another way to overcome test anxiety. Encouragement
from each other helps to increase your confidence.
Applied Technology • 99
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BASIC SCIENTIFIC PRINCIPLES
Applied Technology focuses on:
• Principles related to power sources - for mechanical, electrical, thermal, and fluid
systems
• Principles related to flow - for mechanical, electrical, thermal, and fluid systems
• Principles related to pressure - for mechanical, electrical, thermal, and fluid systems
• Principles related to resistance - for mechanical, electrical, thermal, and fluid systems
The basic scientific principles involved with energy sources, flow, pressure, and resistance
appear below:
Bernoulli’s principle: The faster the flow of air or fluid, the lower the pressure.
Boyle’s law: For a certain amount of gas, at a constant temperature, as the pressure (P)
increases, the volume (V) of the gas decreases so that P times V is constant (k). (PV=k).
Charles’ law: For a certain amount of gas, at a constant pressure, as the absolute
temperature of the gas increases, the volume of the gas also increases. Mathematically
this is: Volume (V) divided by temperature (T) equals a constant (k). V/T=k The
temperature must be on an absolute scale that is in reference to absolute zero.
Hooke’s law: The greater the force exerted on an object, the more it will be moved. For
example, the heavier the weight hanging from a spring, the more the spring will be
stretched.
Newton’s laws of motion
• An object will remain at rest or in uniform motion unless acted upon by an outside
force.
• When a force acts upon an object, it changes the momentum of that object, and
this change is proportional to the applied force and to the time that it acts upon
the object.
• Every action (force) is followed by an equal and opposite reaction (force).
Laws of Thermodynamics
• Energy cannot be created or destroyed.
• Heat energy always flows spontaneously from hot to cold.
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Ohm’s law: Current is directly proportional to the voltage and inversely proportional to
the resistance.
Pascal’s law: Pressure added to a confined fluid at any point instantly appears equally at
all other points and is always at right angles to the containing surfaces.
’s Law
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Applied Technology • 101
REFERENCE
Generalizations that can be made about mechanics:
A machine is something that does work.
Work is done when a force causes an object to move.
Simple machines (gears, pulleys, inclined planes, levers, wheel and axle), which are
described below, make up compound (or complex) machines.
Compound machines include a bicycle, a rod and reel, a typewriter, a can opener, scissors,
a hand drill, a car, a weight machine, and a treadmill.
Gears
• The force that is applied to a driver gear is transferred to a driven gear.
• When two gears of different sizes are meshed together, the smaller gear turns
faster (more rotations per minute) than the larger gear.
• Gears that are meshed together move in opposite directions.
• The direction and speed of the driver gear determines the speed and direction of
gears that are meshed with it.
• Common applications of gears include bicycle sprocket chains, speedometers,
clocks, electric mixers, lawn sprinklers, and egg beaters.
Pulleys
• A pulley is a wheel with a rope, belt, or chain around it.
• Pulleys change the direction of movement and make work easier.
• Fixed pulleys change the direction that something is moved; they do not make
work easier.
• Movable pulleys change the direction that something is moved and make work
easier.
• The more pulleys in the system, the easier it is to do work (pull or lift an object).
• The more pulleys involved in a system, the greater distance must be pulled, but
the easier it is to do work.
• The thinner the windlass (winch), the easier it is to turn.
• In two different sets of pulleys, if the wheels are connected by a shaft and the two
wheels on one pulley are the same size as the two wheels on the other pulley, they
will both turn at the same speed.
• Common pulley applications include crankshafts, sailboats, boat lifts, window
blinds, cranes, elevators, and escalators.
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Inclined Planes
• An inclined plane is a slanted surface that is used to raise or lower heavy objects
from one position to another.
• Inclined planes help reduce the amount of force needed to do a given amount of
work, but require greater distance.
• The steeper the plane, the more difficult the work.
• Wedges are two back-to-back inclined planes.
• Common applications of inclined planes include a screw, a bolt, a drill bit, a
clamp, a car jack, and a screw-on bottle top.
Levers
• A lever is a bar or rod that is free to move or turn on a fulcrum.
• A lever multiplies force, but some distance must be given up.
• The shorter the effort arm, the less force is attained and the greater distance is
attained.
• The longer the effort arm, the more force is attained and the less distance is attained.
• Examples of levers include scissors, a broom, a claw hammer, a nutcracker, a mop,
tongs, a crowbar, a can opener, tweezers, a baseball bat, boat oars, and a car jack
handle.
Wheel and Axle
• A wheel and axle is like a spinning lever (an ice cream machine crank).
• The center of the axle is the fulcrum.
• The wheel is larger than the axle; for one rotation, a point on the edge of the
wheel travels a greater distance than a point on the axle. While the work done
by the axle and the wheel are the same, the greater distance traveled of the
point on the edge of the wheel yields a smaller force at the edge of the wheel
versus the edge of the axle.
• Common wheel and axle applications include a screwdriver, roller skates,
a water-faucet handle, a bicycle pedal, a can opener, and a car steering wheel.
Applied Technology • 103
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Overview of Electricity
Electricity is the continuous flow of electrons, or current, from one atom to another. No
electron flow will occur unless there is a pathway over which the electrons can move.
This flow is similar to a water system, where pipes or hoses move water from storage
tanks to where it is needed. In electrical wiring, the pathway through which electrical
current flows is called a circuit. A simple circuit consists of a power source, conductors,
load, and a device for controlling current. Each is described below.
In buildings, the power source could be the electrical generating stations that pump
electricity into residential and commercial buildings. However, other common sources
of electrical power include small generators and batteries.
Conductors, or wiring, provide a path for the current so that it can travel from one point
to another.
A load is a device through which electricity produces work. For example, a lamp is a load
that, when plugged in and turned on, produces light. Other examples of loads include
heaters, electric motors, and televisions.
Switches (on-off switches) control when electrical current flows through circuits. Fuses
and circuit breakers are protective devices that control current by preventing too much
current from flowing in the circuit, which would damage equipment. When an excessive
amount of electricity passes through them, fuses and circuit breakers “blow” to stop the
flow of electricity through the circuit.
In a circuit, resistance lowers the amount of electrical energy available to do work. Both
wires and load affect resistance. It might be helpful to think of a similar situation with a
hose that is connected to two sprinklers. As water passes through a hose, turns or kinks
in the pathway cause friction (which is resistance) that results in a slower flow. In addition,
when some of the water is diverted to the first sprinkler (which is a load), less water is
available for use in the second sprinkler.
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There are two ways or methods of having current flow. Direct current flows in one
direction. In most cases, direct current is provided to equipment by batteries (flashlights
and portable radios). Alternating current flows in one direction, then reverses to the
other direction. Alternating current is provided to equipment through electrical substations
in buildings. In the United States, common household current reverses itself 60 times
per second. This results in 120v 60 cycle AC. The international reference for cycles is
defined in hertz (one hertz = 1 cycle per second).
Measurement of Electric Current
The rate at which electricity flows is called amperage. It is measured in amperes. A 100watt bulb requires a current of approximately 1 ampere to make it light up completely.
Current flow is measured with an ammeter. Most electrically powered equipment indicate
the amount of current needed to operate it properly.
Measurement of Electrical Pressure
Pressure is applied to electrons to force them to move through a conductor and around a
circuit. This pressure is measured in volts. The pressure, or voltage, is available in wiring
circuits all of the time - whether or not electrical equipment is being used. Voltage is
measured with a voltmeter.
Calculation of Power
The amount of power derived from an electrical device or system is its wattage. In other
words, it is the product obtained from electrical energy; it is the power that we put into
use. For example, the electric company sells electrical energy. Electrical energy or power
is measured in watts and can be calculated as follows:
For direct-current circuits: volts × amperes = watts
For alternating-current circuits: volts × amperes × power factor = watts
NOTE: Power factors range from 0-1. Large equipment (an electric heater) may have a
power factor as high as 1; small equipment (a small motor) may have a power factor as
low as .25.
Applied Technology • 105
REFERENCE
Ohm’s law
Ohm’s law is a simple formula used to describe the relationship between current (flow),
voltage (pressure), and resistance of an electrical circuit. Each component interacts to
affect the operation of a circuit. In other words, because voltage pushes current through
a resistance, a change in any of the components will result in a change in the others. The
following three equations are Ohm’s law rearranged to solve for each of the quantities:
Current = Voltage ÷ Resistance I = E/R
amps = volts ÷ ohms
An increase in voltage causes an increase in
electrical current flow. An increase in circuit
resistance causes a decrease in electrical current
flow.
Voltage = Current × Resistance E = I × R
volts = amps × ohms
An increase in current causes an increase in
voltage. An increase in resistance causes an
increase in voltage.
Resistance = Voltage ÷ Current R = E/I
ohms = volts ÷ amps
106 • Applied Technology
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Generalizations that can be made about electricity:
• The longer the wire, the greater the resistance; the thinner the wire, the greater
the resistance.
• An increase in temperature of a wire causes an increase in resistance.
• An ordinary electrical cord has two wires; one for the flow of current from the
power source and the other for the return or ground.
• The voltage (pressure) and current (flow of electricity) directly affect how much
power is available to do work. Less energy source or lower flow will result in less
electrical power being produced.
• A series circuit has only one path for the flow of current. In a series circuit, objects
are placed one after another and the current flows through each of them in
succession. The current is the same throughout, however, and the voltage is divided
among the objects in the circuit.
• In a parallel circuit, there are 2 or more paths, or branches, for the flow of current.
The current will divide and flow through each of the paths simultaneously. Every
branch has the same voltage and - if the appliances are all the same - will have the
same amount of current. The total circuit resistance is less than any one branch.
• When batteries are connected in a series, the current is the same; the total voltage
is the sum of the voltage of each battery. The terminals are connected +, -, +, -,
and so on.
• When batteries are connected in parallel, the total current is the sum of the currents
in each battery; the total voltage is the same as that of one cell. The terminals are
connected +, +, +, and -, -, -.
Applied Technology • 107
REFERENCE
Generalizations that can be made about heat:
• Heat travels through conductors (e.g., metal) better than through insulators (e.g.,
wood).
• Dark-colored surfaces absorb more heat than light-colored surfaces.
• Rough or dull surfaces absorb more heat than smooth or shiny surfaces.
• When friction causes heat, the object that is in constant contact gets hotter than
the movable object. (For example, the wood being cut gets hotter than the saw
blade; car brake shoes get hotter than the wheel).
Generalizations that can be made about fluids:
Pressure
• The amount of pressure exerted by a fluid depends upon the height and the density
of that fluid and is independent of the shape of the container that is holding the
fluid.
• The deeper the fluid, the greater the pressure it exerts.
• The denser the fluid, the greater the pressure it exerts (salt water is denser than
fresh water).
• Fluids seek equilibrium - they seek their own level; a fluid will flow from a place of
high pressure to a place of low pressure.
• A fluid can never rise higher than its source without an external force (a pump).
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Evaporation
• The higher a liquid’s temperature, the faster it will evaporate.
• The lower a liquid’s pressure, the faster the liquid will evaporate.
• The more area of liquid that is exposed to air, the faster the liquid will evaporate.
• The more circulation of air above a liquid, the faster the liquid will evaporate.
Boiling Point
• Increased pressure on a liquid raises the liquid’s boiling point.
• Decreased pressure on a liquid lowers the liquid’s boiling point.
Applied Technology • 109
REFERENCE
BIBLIOGRAPHY
Adkinson, S., & Fleer, M. (Eds.). (1995). Science with reason. London: Hodder and
Stoughton Educational.
American Association for the Advancement of Science (1993). Benchmarks for science
literacy: A project 2061 report. New York: Oxford University Press.
American Association for the Advancement of Science (1990). Science for all Americans:
A project 2061 report on literacy goals in science, mathematics, and technology. New York:
Oxford University Press.
Bransford, J., & Stein, B. (1984). The IDEAL problem solver: A guide for improving
thinking, learning, and creativity. New York: W. H. Freeman and Co.
Ohio Department of Education (1994). Ohio’s competency-based science model: Scientific
literacy for the 21st century. Columbus, OH: State Board of Education.
National Council of Teachers of Mathematics (1993). Curriculum and evaluation
standards for school mathematics. Reston, VA: NCTM.
National Research Council (1996). National science educational standards. Washington,
DC: National Academy Press.
The Secretary’s Commission on Achieving Necessary Skills (1992). Learning a living:
A blueprint for high performance: A SCANS report for America 2000. Washington, DC:
U.S. Department of Labor.
110 • Applied Technology
ANSWERS TO POP QUIZ QUESTIONS
Page 28 — Compressor – a device that pressurizes gases
Page 30 — IDEAL Strategy
• Identify the problem
• Define and represent that problem
• Explore alternatives
• Act on a plan
• Look at the result
Applied Technology • 111
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