Technology and Livelihood Education
AREA:
BASIC ELECTRONICS
LET Competencies:
1. Apply the Fundamentals of Electronics in Household Appliances
2. Identify Electronic Tools and Components used in Common
Household Appliances
3. Interpret Electronics Schematic Diagram
4. Analyze Basic Electronic Circuit Trouble in Appliances
5. Appraise the Result of Simple Electronic Circuit Repair
PART I: CONTENT UPDATE
FUNDAMENTALS OF ELECTRONIC
ELECTRONICS
Electronics is the branch of science and engineering concerned with the
theory, design, and the use of devices which involve the transmission of power
by utilizing electron emission or absorption. Electronics includes all aspects of
photoelectric cells, transistors, circuits, cathode-ray tubes, electron tubes,
oscilloscopes, electron microscopes, broadcasting, radio, television, telephone,
and many other industries.
DEFINITION OF TERMS
1. Electronic components - is any physical entity in an electronic system
whose intention is to affect the electrons or their associated fields in a desired
manner consistent with the intended function of the electronic system
2. Electrical Circuit - is a network that has a closed loop, giving a return path
for the current
3. Network - is a connection of two or more components, and may not
necessarily be a circuit
4. Conductors – are metals and other substances where electrons can move
freely
5. Insulators – substances where electrons cannot move freely
6. Transformer – is an electronic devised used in producing desired voltage
7. Inductors – the choke or coil in a circuit that oppose changes in electric
current
8. Semiconductors – a group that are neither good conductors nor good
insulators
BASIC ELECTRONIC TOOLS
1. Electric Drill and Drill Bits - in the range of 1/8 inch to 1/2 inch will come in
handy when you need to drill holes on the printed circuit board that has been
etched. Drilling of plastic or metal enclosure that houses the printed circuit
board are sometimes necessary.
2. Soldering Iron - a 20 Watt to 30 Watt soldering iron with tips of 1/8 inch to
1/2 inch can be used for soldering of through hole components. Soldering of
surface mount components may require smaller tips depending on the sizes
of the components. Soldering iron normally will last a long time if it is taken
care of properly by keeping the tips clean and well tinned.
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3. Disordering Pump - A pump aids in the removal of the liquid solder. It is
operated by a spring-loaded vacuum pump and controlled by a simple trigger.
4. Vacuum Pick Up Tool - A pick and place head for transferring die or chips
containing electronic circuitry from waffle packs to substrates prior to lead
bonding operations.
5. Soldering Stand - It keeps the iron away from flammable materials
6. Helping Hand Tool - A crucial tool in doing successful electronics work. It
consists of a weighted base, arms ending in alligator clips, magnifying glass
and flexible joint.
7. Wire strpper - is used to strip off wire insulator from its conductor before it is
used to connect to another wire or soldered into the printed circuit board.
Some wire stripper or wire cutter has a measurement engraved on it to
indicate the length that will be stripped.
8. Long nose Pliers – a 4-inch long nose pliers will come in handy when you
need to hold components that have short leads that need to be soldered onto
the PCB but will be too hot to handle with bare hands. It will also be useful to
hold the component that needs to be de-soldered from the board.
9. Side-Cutting Pliers - 4-inch side cutting pliers will come in handy as one of
the electronic tools when one need to trim off excess component leads on the
printed circuit board. It can also be used to cut wires into shorter length before
being used.
10. Small tweezers - is used to hold small components especially when doing
soldering and de-soldering of surface mount components.
11. Allen Wrench set - set is sometimes used to unscrew or screw Allen type of
screws.
12. Philips Head Screwdrivers -various sizes of Philips head screwdrivers will
be handy as a lot of electronics projects that use screws are Philips Head
type.
13. Flat Head Screwdrivers - of various sizes are also necessary as many
screws that are used are of this type.
14. Hammer - a small, light hammer will be useful when assembling projects that
involved casing.
15. Socket wrench - sets that include nut drivers, hex drivers, and starters in
assorted sizes will come in handy during the assembly work of electronics
project.
16. Pocket Knife - will be useful when one need to cut PCB, wires or remove
some cooper from the printed circuit board.
Maintenance Tips of Electronic Tools
Good quality tools that are being purchased can last a lifetime if they are
taken care of properly.
1. Ensure that the tools are used only for their intended purposes.
2. Keep them lubricated with a light film of oil to inhibit rust.
3. Keep the tools clean and sharp; keep the soldering tips clean and well tinned.
4. Ensure that proper uses of the tools are always adhered to by following the
instructions of using the tools.
ELECTRONIC COMPONENTS
These are the basic electronic element usually packaged in a discrete
form with two or more connecting leads or metallic pads in which intended to be
connected together, usually by soldering to a printed circuit board, to create an
electronic circuit with a particular function (for example an amplifier, radio
receiver, or oscillator) may be packaged singly (resistor, capacitor, transistor,
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diode etc.) or in more or less complex groups as integrated circuits (operational
amplifier, resistor array, logic gate etc.)
CAPACITORS
Capacitor is a device able to temporarily store electricity. It was invented
by Ewald Georg von Kleist (October 1745). These relatively simple components
consist of two pieces of conducting material (such as metal) separated by a nonconducting (insulating) material called a dielectric. When a voltage potential
difference exists between the conductors, an electric field is present in the
dielectric. This field stores energy and produces a mechanical force between the
plates. The effect is greatest between wide, flat, parallel, narrowly separated
conductors.
Types of Capacitor
1. Electrolytic Capacitor (Electrochemical Type Capacitor)
2. Tantalum Capacitor
3. Ceramic Capacitor
4. Polystyrene Film Capacitor
5. Mica Capacitor
6. Metallized Polyester Capacitor
7. Variable Capacitor
8. Trimmer Capacitor
DIODE
This device is used to limit the movement of electricity to move in one
specific direction. Some diodes are also designed to produce light or to act as a
switch in an electrical circuit. It has two active electrodes between which the
signal of interest may flow, and most are used for their unidirectional electric
current property. Diode also allows an electric current to flow through them in
only one direction. They are also known as rectifiers. It can be used to change
alternating currents (ones flowing back and forth round a circuit, constantly
swapping direction) into direct currents (ones that always flow in the same
direction).
Types of Diode
1. Light Emitting Diode (LED)
2. Avalanche Diode
3. Laser Diode
4. Schottky Diodes
5. Zener diode
6. Photodiode
7. Varicap Diode or Varactor Diode Rectifier Diode
TRANSISTOR
An electrical circuit needs to have switches to control the current. In
electronic equipment, the most useful kind of switch is the transistor. Transistors
is invented by William Shockley which considered by many as the father of
transistor. This device commonly varies in composition and in the arrangement of
the components. It is use to amplify or switch electronics signals which is made
of a solid piece of a semiconductor material, with at least three terminals for
connection to an external circuit. The diagram below shows the components in
one kind of transistor.
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Gate: The post of a transistor that
receives the current used to turn the
switch on completing the circuit so
electricity can flow
Source: The post of a transistor where the
current in the closed circuit enters the
transistor
Drain: The post of a transistor that passes
the current from the transistor and on
through the closed circuits
A transistor is turned on when an
electrical charge is applied to the gate.
This changes the electrical charge in
the transistor to allow electrons to
move from the source to the drain. If
the transistor is turned off—no
electrical charge on the gate—the
pathway of the circuit is broken and the
current stops.
RESISTOR
This device is the simplest components in any circuit. With a measurable
ability to resist the flow of electrons used to control the strength of the current in a
circuit. Resistors come in many different shapes and sizes. Variable resistors
(also known as potentiometers) have a dial control on them so they change the
amount of resistance when you turn them.
Europe Resistor Symbol
United State Resistor Symbol
Type of Resistor
1. Variable Resistor (Potentiometer)
2. Variable Resistor (Preset)
3. Carbon Composition Resistor
4. Film or Cermet Resistor
5. Wire-Wound Resistors
6. Metal oxide film resistors
7. Vitreous Enamel Resistors
8. Cement resistors
9. Semiconductor Resistors
RESISTOR COLOR CODING
COLOR
Black
Brown
Red
Orange
1ST band
0
1
2
3
2nd band
0
1
2
3
3rd band
4th band
Temp.
(multiplier)
(tolerance)
Coefficient
+ 1% (F)
+ 2% (G)
100 ppm
50 ppm
15 ppm
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Yellow
Green
Blue
Violet
Gray
White
Gold
Silver
None
4
5
6
7
8
9
4
5
6
7
8
9
25 ppm
+ 0.5 % (D)
+ 0.25% (C)
+ 0.1% (B)
+ 0.05% (A)
+ 5% (J)
+ 10% (K)
+ 20% (M)
Example
TYPES OF CIRCUIT BOARD
1. Breadboard
- Temporary, no soldering required
- This is a way of making a temporary circuit,
for testing purposes or to try out an idea.
- No soldering is required and all the
components can be re-used afterwards.
- It is easy to change connections
and replace components
2. Strip board
- Permanent, soldered
- Strip board has parallel strips of
copper track on one side. The strips
are 0.1" (2.54mm) apart and there
are holes every 0.1" (2.54mm).
- Strip board requires no special
preparation other than cutting to
size. It can be cut with a junior
hacksaw, or simply snap it along the
lines of holes by putting it over the
edge of a bench or table and
pushing hard.
3. Printed Circuit Board
-
Permanent, soldered
Printed circuit boards have copper
tracks connecting the holes where
the components are placed.
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ELECTRONIC SCHEMATIC DIAGRAM
Simple Amplifier Circuit Diagram
ELECTRONIC SYMBOLS
1. Resistor
Component
Circuit Symbol
Resistor
Variable Resistor
(Rheostat)
Variable Resistor
(Potentiometer)
Variable Resistor
(Preset)
2. Capacitors
Component
Capacitor
Circuit Symbol
Physical circuit
Function of Component
A resistor restricts the flow of
current, for example to limit the
current passing through an LED.
A resistor is used with a
capacitor in a timing circuit.
This type of variable resistor
with 2 contacts (a rheostat) is
usually used to control current.
Examples include: adjusting
lamp brightness, adjusting motor
speed, and adjusting the rate of
flow of charge into a capacitor in
a timing circuit.
This type of variable resistor
with 3 contacts (a potentiometer)
is usually used to control
voltage. It can be used like this
as a transducer converting
position (angle of the control
spindle) to an electrical signal.
This type of variable resistor (a
preset) is operated with a small
screwdriver or similar tool. It is
designed to be set when the
circuit is made and then left
without further adjustment.
Presets are cheaper than
normal variable resistors so they
are often used in projects to
reduce the cost.
Function of Component
A capacitor stores electric
charge. A capacitor is used with
a resistor in a timing circuit. It
can also be used as a filter, to
block DC signals but pass AC
signals.
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Capacitor,
polarized
A capacitor stores electric
charge. This type must be
connected the correct way
round. A capacitor is used with a
resistor in a timing circuit. It can
also be used as a filter, to block
DC signals but pass AC signals.
Variable
Capacitor
A variable capacitor is used in a
radio tuner.
Trimmer
Capacitor
This type of variable capacitor (a
trimmer) is operated with a small
screwdriver or similar tool. It is
designed to be set when the
circuit is made and then left
without further adjustment.
3. Diodes
Component
Circuit Symbol
Diode
LED
Light Emitting
Diode
4.
Function of Component
A device which only allows
current to flow in one direction.
A transducer which converts
electrical energy to light.
Zener Diode
A special diode which is used to
maintain a fixed voltage across
its terminals.
Photodiode
A light-sensitive diode.
Transistor
Component
Circuit Symbol
Function of Component
Transistor NPN
A transistor amplifies current. It
can be used with other
components to make an
amplifier or switching circuit.
Transistor PNP
A transistor amplifies current. It
can be used with other
components to make an
amplifier or switching circuit.
Phototransistor
A light-sensitive transistor.
5. Audio and Radio Devices
Component
Circuit Symbol
Function of Component
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Microphone
A transducer which converts
sound to electrical energy.
Earphone
A transducer which converts
electrical energy to sound.
Loudspeaker
A transducer which converts
electrical energy to sound.
Piezo
Transducer
A transducer which converts
electrical energy to sound.
Amplifier
(general symbol)
Aerial
(Antenna)
6. Meters and Oscilloscope
Component
Circuit Symbol
Voltmeter
Ammeter
Galvanometer
Ohmmeter
Oscilloscope
7. Sensors (input devices)
Component
Circuit Symbol
An amplifier circuit with one
input. Really it is a block
diagram symbol because it
represents a circuit rather than
just one component.
A device which is designed to
receive or transmit radio signals.
It is also known as an antenna.
Function of Component
A voltmeter is used to measure
voltage. The proper name for
voltage is 'potential difference',
but most people prefer to say
voltage.
An ammeter is used to measure
current.
A galvanometer is a very
sensitive meter which is used to
measure tiny currents, usually
1mA or less.
An ohmmeter is used to
measure resistance. Most
multimeters have an ohmmeter
setting.
An oscilloscope is used to
display the shape of electrical
signals and it can be used to
measure their voltage and time
period.
Function of Component
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A transducer which converts
brightness (light) to resistance
(an electrical property).
LDR = Light Dependent Resistor
A transducer which converts
temperature (heat) to resistance
(an electrical property).
LDR
Thermistor
8. Logic Gates
Gate
Traditional
Type
Symbol
NOT
AND
NAND
OR
NOR
EX-OR
EXNOR
IEC Symbol
Function of Gate
A NOT gate can only have
one input. The 'o' on the
output means 'not'. The
output of a NOT gate is the
inverse (opposite) of its
input, so the output is true
when the input is false. A
NOT gate is also called an
inverter.
An AND gate can have two
or more inputs. The output
of an AND gate is true when
all its inputs are true.
A NAND gate can have two
or more inputs. The 'o' on
the output means 'not'
showing that it is a Not AND
gate. The output of a NAND
gate is true unless all its
inputs are true.
An OR gate can have two
or more inputs. The output
of an OR gate is true when
at least one of its inputs is
true.
A NOR gate can have two
or more inputs. The 'o' on
the output means 'not'
showing that it is a Not OR
gate. The output of a NOR
gate is true when none of its
inputs are true.
An EX-OR gate can only
have two inputs. The output
of an EX-OR gate is true
when its inputs are different
(one true, one false).
An EX-NOR gate can only
have two inputs. The 'o' on
the output means 'not'
showing that it is a Not EXOR gate. The output of an
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EX-NOR gate is true when
its inputs are the same
(both true or both false).
BASIC ELECTRONIC CIRCUIT TROUBLE IN APPLIANCES
1. Broken wiring inside cord set - internal breaks in the conductors of cord
sets or other connecting cords caused by flexing, pulling, or other long term
abuse. This is one of the most common problems with vacuum cleaners
which tend to be dragged around by their tails.
2. Bad internal connections - broken wires, corroded or loosened terminals.
Wires may break from vibration, corrosion, poor manufacturing, as well as
thermal fatigue. The break may be in a heating element or other
subassembly. In many cases, failure will be total as in when one of the AC
line connections falls off. At other times, operation will be intermittent or
erratic - or parts of the appliance will not function. For example, with a blow
dryer, the heating element could open up but the fan may continue to run
properly.
3. Short circuits – When two wires touching or contacting the metal case of an
appliance happens too often. Partially, this is due to the shoddy
manufacturing quality of many small appliances like toaster ovens. These
also have metal (mostly) cabinets and many metal interior parts with sharp
edges which can readily eat through wire insulation due to repeated
vibrations, heating and cooling cycles, and the like.
A short circuit may develop with no operational problems - but the case of the
appliance will be electrically 'hot'. This is a dangerous situation. Large
appliances with 3 wire plugs - plugged into a properly grounded 3 wire circuit would then blow a fuse or trip a circuit breaker. However, small appliances
like toaster, broilers, irons, etc., have two wire plugs and will just set there
with a live cabinet.
4. Worn, dirty, or broken switches or thermostat contacts - These will result
in erratic or no action when the switch is flipped or thermostat knob is turned.
In many cases, the part will feel bad - it won't have that 'click' it had when new
or may be hard to turn or flip. Often, however, operation will just be erratic jiggling the switch or knob will make the motor or light go on or off, for
example.
5. Gummed up lubrication, or worn or dry bearings - Often, due to
environmental conditions (dust, dirt, humidity) or just poor quality control
during manufacture, a motor or fan bearing will gum up or become dry
resulting in sluggish and/or noisy operation and overheating. In extreme
cases, the bearing may seize resulting in a totally stopped motor. If not
detected, this may result in a blown fuse (at the least) and possibly a burnt
out motor from the overheating.
6. Broken or worn drive belts or gears - rotating parts do not rotate or turn
slowly or with little power even through the motor is revving its little head off.
When the brush drive belt in an upright vacuum cleaner breaks, the results
are obvious and the broken belt often falls to the ground (to be eaten by the
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dog or mistaken for a mouse tail. However, there are often other belts inside
appliances which will result in less obvious consequences when they loosen
with age or fail completely.
7. Broken parts - plastic or metal castings, linkages, washers, and other
'doodads' are often not constructed quite the way they used to be. When any
of these fail, they can bring a complicated appliance to its knees. Failure may
be caused by normal wear and tear, improper use, accidents, or shoddy
manufacturing.
8. Insect damage - Many appliances make inviting homes for all sorts of multilegged creatures. Evidence of their visits or extended stays will be obvious
including frayed insulation, short circuits caused by bodily fluids or entire
bodies, remains of food and droppings. Even the smallest ventilation hole can
be a front door.
SIMPLE ELECTRONIC CIRCUIT REPAIR
1. Broken wiring inside cord set
If the problem is intermittent, plug the appliance in and turn it on. Then try
bending or pushing the wire toward the plug or appliance connector end to see if
you can make the internal conductors touch at least momentarily. If the cord set
is removable, test between ends with a continuity checker or multimeter on the
low ohms scale. If it is not detachable, open the appliance to perform this test.
2. Bad internal connections
In many cases, a visual inspection with some careful flexing and prodding
will reveal the location of the bad connection. If it is an intermittent, this may need
to be done with a well insulated stick while the appliance is on and running.
When all else fails, the use of a continuity checker or multimeter on the low ohms
scale can identify broken connections which are not obviously wires visibly
broken in two. For testing heating elements, use the multimeter as a continuity
checker may not be sensitive enough since the element normally has some
resistance.
3. Short circuits
Visually inspect for bare wires or wires with frayed or worn insulation
touching metal parts, terminals they should not be connected to, or other wires.
Use a multimeter on the high ohms scale to check between both prongs of the
AC plug and any exposed metal parts. Try all positions of any power or selector
switches. Any resistance measurement less than 100K ohms or so is cause for
concern - and further checking. Also test between internal terminals and wires
that should not be connected together.
4. Worn, dirty, or broken switches or thermostat contacts
Where there is a changed feel to the switch or thermostat with an
associated operational problem, there is little doubt that the part is bad and must
be replaced. Where this is not the case, label the connections to the switch or
thermostat and then remove the wires. Use the continuity checker or ohmmeter
across each set of contacts. They should be 0 ohms or open depending on the
position of the switch or knob and nothing in between. In most cases, you should
be able to obtain both readings. The exception is with respect to thermostats
where room temperature is off one end of their range. Inability to make the
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contacts open or close or erratic intermediate resistances which are affected by
tapping or jiggling are a sure sign of a bad set of contacts.
5. Gummed up lubrication, or worn or dry bearings
If the appliance does not run but there is a hum (AC line operated
appliances) or runs sluggishly or with less power than you recall when new,
lubrication problems are likely. With the appliance unplugged, check for free
rotation of the motor(s). In general, the shaft sticking out of the motor itself should
turn freely with very little resistance. If it is difficult to turn, the motor bearings
themselves may need attention or the mechanism attached to the motor may be
filled with crud. In most cases, a thorough cleaning to remove all the old dried up
and contaminated oil or grease followed by relubing with similar oil or grease as
appropriate will return the appliance to good health. Don't skimp on the
disassembly - total cleaning will be best. Even the motor should be carefully
removed and broken down to its component parts - end plates, rotor, and stator,
brushes (if any) in order to properly clean and lubricate its bearings.
6. Broken or worn drive belts or gears
Except for the case of a vacuum cleaner where the belt is readily
accessible, open the appliance. A good rubber belt will be perfectly elastic and
will return to its relaxed length instantly when stretched by 25 percent and let go.
It will not be cracked, shiny, hard, or brittle. A V-type belt should be dry (no oil
coating), undamaged (not cracked, brittle, or frayed), and tight (it should deflect
1/4" to 1/2" when pressed firmly halfway between the pulleys).
7. Broken parts
In many cases, the problem will be obvious. Where it is not, some careful
detective work - putting the various mechanisms through their paces - should
reveal what is not functioning. Although replacement parts may be available, you
can be sure that their cost will be excessive and improvisation may ultimately be
the best approach to repair.
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PART II: ANALYZING TEST ITEMS
Competency No. 1 Apply the Fundamentals of Electronics in Household
Appliances
1. What branch of physics refers to the flow of electron through nonmetal
conductors?
A. Mechanics
C. Electricity
B. Physics
D. Electronics
The correct answer is D. Electronics
Option A deals with energy and forces and their effects on the bodies
Option B refers to experimental science
Option C refers to the basic forms of energy
Competency No. 2 Identify Electronic Tools and Components used in Common
Household Appliances
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2. It is an electronic tool that is use to strip off wire insulator from its
conductor.
A. wire stripper
C. small tweezers
B. socket wrench
D. long nose pliers
The correct answer is A. wire stripper
Option B used for gripping
Option C is small tweezers it is used to hold small components
Option D is long nose pliers it is used to hold components that have
short leads
Competency No. 3 Interpret Electronics Schematic Diagram
3. LDR refers to?
A. Light Dependent Resistor
B. Light Devices Resistor
C. Light Diode Resistant
D. Light Depending Resistor
The correct answer is A. Light Dependent
Resistor Option B does not apply to the question
Option C does not apply to the question Option D
does not apply to the question
Competency No. 4 Analyze Basic Electronic Circuit Trouble in Appliances
4. Circuit troubles such as broken wires, corroded or loosened
terminals show:
A. short circuits
C. broken wiring
B. broken parts
D. bad internal connections
The correct answer is D. bad internal connections
Option A is circuit trouble that caused contraction of metal case
Option B is circuit trouble that caused linkages and complication to appliances
Option C is circuit trouble that caused internal breaks in the conductors
Competency No. 5 Appraise the Result of Simple Electronic Circuit Repair
5. What should be the repair in a broken wiring?
A. bends or pushes the wire toward the plug or appliance connector end
B. label the connections to the switch or thermostat
C. inspect for bare wires or wires with frayed or worn insulation
D. use the continuity checker or ohmmeter across each set of contacts
The correct answer is A. Bend or pushes the wire toward the plug or appliance
connector end
Option B is used as a repair for worn or broken switches
Option C is used as repair in short circuits
Option D is used as a repair for broken circuit
6. The symbol for earphone
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a.
c.
b.
d.
7. Which voltage source converts chemical energy to electrical energy?
a. Electrical generator
c. Battery
b. Solar cell
d. Electronic power supply
8. What is the color code in 5 band for a 150 M + 10% resistor?
a. Brown, Green, Black, Blue, and Gold
b. Brown, Green, Black, Yellow, and Gold
c. Brown, Green, Black, Blue, and Silver
d. Brown, Green, Black, Yellow, and Silver
9. Which electronics material opposes the movement of free electrons?
a. Element
c. Conductor
b. Insulator
d. Semiconductor
10. The logic gate that will have HIGH or "1" at its output when any one of
its inputs is HIGH is a(n):
a. OR Gate
c. Nor Gate
b. Ex-Or Gate
d. Ex-Nor Gate
11. Which among the types of circuit board can easily change the
connections of components?
a. Strip board
c. Breadboard
b. Printed circuit board
d. None of the above
12. Which is the symbol for amplifier?
a.
c.
b.
d.
13. What is the common characteristic of strip board and printed circuit board?
a. temporary circuit board
c. no soldering required
b. permanent circuit board
d. requires no special preparation
14. Which of the following is not an electronics component?
a. diode
c. resistors
b. capacitors
d. power
15. What does LED refers to?
a. Light Emitting Diode
b. Light Emission Devices
c. Light Emitting Devices
d. Light Emission Diode
16. Which is NOT true about proper maintenance of electronic tools?
a. Ensure that the tools are used only for their intended purposes.
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b. Keep the tools lubricated with soap and water inhibits rust.
c. Keep the tools clean and sharp.
d. Keeps the soldering tips clean and well tinned.
17. The symbol for transistor PNP
a.
c.
b.
d.
18. If a signal passing through a gate is inhibited by sending a low into one
of the inputs, and the output is HIGH, the gate is a(n):
a. OR Gate
c. AND Gate
b. NOR Gate
d. NAND Gate
19. One of the most common problems with vacuum cleaners is broken
wiring inside cord set. This is due to _____________.
a. flexing, wiring, long term abuse
c. poor manufacturing
b. vibration, corrosion
d. dust, dirt, humidity
20. This symbol is used to measure voltage.
a.
b.
c.
d.
21. A device which is designed to receive or transmit radio signals.
a. Amplifier
c. Antenna
b. Ammeter
d. Piezo Transducer
22. What electronic component is commonly used to amplify or
switch electronic signals?
a. capacitor
c. diode
b. transistor
d. resistor
23. Use to assemble electronics appliances and project.
a. electronics tools
c. electronics components
b. electronics unit
d. electrical network
24. When using soldering iron in soldering surface mount component it
requires ___.
a. bigger tips
c. narrow tips
b. smaller tips
d. wider tips
25. What is the color code in 5 band for a 63 M and 10% resistor?
a. Blue, Orange, Black, Green and Gold
b. Blue, Orange, Black, Green and Silver
c. Blue, Yellow, Black, Green and Silver
d. Blue, Red, Black, Green and Silver
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Technology and Livelihood Education
PART III: ENHANCING TEST TAKING SKILLS
1. What input values will cause an AND logic gate to produce a
HIGH output?
a. At least one input is LOW.
b. At least one input is HIGH.
c. All inputs are LOW.
d. All inputs are HIGH.
2. Ohm's law describes the mathematical relationship between
a. resistance, voltage, and current
b. resistor size and resistor value
c. ohms, kilohms, and megohms
d. none of the above
3. One of the most common applications of a potentiometer is as
an adjustable voltage divider, also known as
a. divider control
c. voltage control
b. volume control
d. current control
4. What is this symbol
a. capacitor
b. variable capacitor
?
c. polarized capacitor
d. timmer capacitor
5. What is the color code for a 220 5% resistor?
a. Red, Red, Brown, Silver
b. Red, Red, Brown, Gold
c. Red, Red, Black, Gold
d. Orange, Orange, Black, Gold
6. Component that store electrical charge in an electrical field.
a. capacitors
c. resistors
b. diode
d. transistor
7. What electronic circuit trouble is affected of environmental condition such
as dust, dirt, and humidity?
a. broken wiring inside cord set
c. short circuits
b. gummed up lubrication
d. insect damage
8. It is used to connect the holes where components are placed in a
printed circuit board.
a. terminal strip
c. phenolic board
b. copper tracks
d. copper board
9. A NAND gate has:
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Technology and Livelihood Education
a. LOW inputs and a HIGH output
output
b. LOW inputs and a LOW output
c. HIGH inputs and a HIGH
d. None of these above
10. This symbol is used to measure current.
a.
c.
b.
d.
11. What is the resistor value of Blue, Black,
Silver?
a. 60 K + 5%
c. 60 K + 10%
b. 50 K + 5%
d. 50 K + 5%
Orange and
12. Electronic tools can last lifetime if they are ___________________.
a. used in many purposes
b. inhibit rust because they are not lubricated
c. properly use based from the instructions given
d. clean once in a while
13. A _____ is a device that resists the flow of charge.
a. Resistor
c. Diode
b. Buffer
d. Microfarad (or µF;)
14. In logic gate, the output will be a LOW for any case when one or more
inputs are zero in a(n):
a. OR Gate
b. AND Gate
c. NAND Gate
d. NOT Gate
15. It is used to display the shape of electrical signals and it can be used to
measure their voltage and time period.
a. Galvanometer
b. Ohmmeter
c. Voltmeter
d. Oscilloscope
16. What do you call a diagram that shows the electrical connections of a
circuit's components?
a. Schematic Diagram
b. Block Diagram
c. Pictorial Diagram
d. Electronic Diagram
17. Which of these is the function of zener diode?
a. allows current to flow in one direction
b. converts electrical energy to light
c. maintain a fixed voltage across its terminals
d. produced a light-sensitive diode
18. A device designed to receive or transmit radio signals.
a. loudspeaker
c. microphone
b. antenna
d. amplifier
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Technology and Livelihood Education
19. What kind of network does electric circuit has?
a. opened loop
c. closed loop
b. one loop
d. two loop
20. In logic gates, the output is true when its inputs are different.
a. OR Gate
c. EX-OR Gate
b. NOR Gate
d. EX-NOR Gate
21. A kind of diode which converts electrical energy to light.
a. Rectifier diode
c. Varicap Diode
b. Zener Diode
d. Light Emitting Diode
22. A very sensitive meter which is used to measure tiny currents
a. Galvanometer
c. Ohmmeter
b. Ammeter
d. Volt Meter
23. It is used to limit the movement of electricity to move in one
specific direction.
a. Capacitor
c. Transistor
b. Resistor
d. Diode
24. Which type of logic gate has one input?
a. NOT Gate
c. AND Gate
b. NAND Gate
d. NOR Gate
25. A standard wattage for soldering iron is
a. 20W to 10W
c. 20W to 40W
b. 20W to 30 W
d. 20W to 50W
ANALYZING TEST ITEMS
1. D
2. A
3. A
4. D
5. A
6. B
7. C
8. A
9. D
10. A
11. C
ANSWER
ENHANCING TEST TAKING SKILLS
1. D
2. A
3. B
4. C
5. B
6. A
7. B
8. B
9. A
10. B
11. C
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Technology and Livelihood Education
12. C
13. B
14. B
15. A
16. B
17. B
18. D
19. A
20. D
21. C
22. C
23. A
24. B
25. B
12. C
13. A
14. B
15. D
16. A
17. C
18. B
19. C
20. C
21. D
22. A
23. D
24. A
25. B
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