SHPE Foundation
Online SHPE Jr. Member
Activities
TeachEngineering Hands-on
Activity:
*Light Your Way
TeachEngineering Digital Library:
teachengineering.org
SHPE Foundation
Online SHPE Jr. Member Activities
TeachEngineering Digital Library
http://www.teachengineering.org
• The TeachEngineering digital library provides over
1350 free engineering lessons and activities.
• Engineering lessons and activities connect realworld experiences with curricular content already
taught in K-12 classrooms.
• TeachEngineering's comprehensive curricula are
hands-on, inexpensive, and relevant to students'
daily lives.
SHPE Foundation
Online SHPE Jr. Member Activities
Light Your Way
Reference Activity on TeachEngineering
• Learn about circuitry through the design and construction of
a portable flashlight!
• Engineering focus:
o Engineering Design Process
• Using limited materials, brainstorm, design, test and redesign
until you have a functioning flashlight.
• Learning objectives:
o Design and construct a working portable flashlight.
o Define, recognize and assemble series circuits.
o Explain the path of electrical charge through your circuit.
o Describe the engineering process behind designing a flashlight.
SHPE Foundation
Online SHPE Jr. Member Activities
Light Your Way
• Suggested time: 60 minutes
• Materials
o 2 D-cell batteries
o 5 pieces of insulated copper
wire (various lengths; available
at hardware stores)
o 1 #40 bulb (available at
hardware stores)
o 1 bulb holder (available at
hardware stores)
o 1 cardboard paper towel or
wrapping paper tube
o reflective material (aluminum
foil, small pie tins, foil muffin cups,
etc.)
o thumb tacks
o rubber bands
o masking tape
o wire strippers or medium-grade
sandpaper (to remove insulation
from wire ends)
o wire cutters
o scissors
Optional materials:
o thin flat strips of wood or plastic
o switch (available at Radio Shack
or other electronics stores) or a
variety of materials to make a
switch (paper clips, aluminum
foil, nails, coins, insulated wire
(possibly of varying gauges, keys,
etc.
SHPE Foundation
Online SHPE Jr. Member Activities
Light Your Way
Engineering Connection (Real World Application):
• When electrical engineers design electrical equipment, they figure out
the optimum circuitry design for the situation, whether it is the
installation of solar panels, design of electric cars, behavior of traffic
signals, hair dryer on/off switch, turn indicator lights on a vehicle or
even a simple flashlight. They decide between creating a parallel or
series circuit, or they often create a complex circuit system composed
of both types.
Solar panels
Electric Car
Flashlight
SHPE Foundation
Online SHPE Jr. Member Activities
Light Your Way
Vocabulary
Terms
Alternating
current (AC)
Circuit diagram
Direct current
(DC)
Energy transfer
Load
Parallel circuit
Resistor
Series circuit
Definitions
An electric current that reverses direction at regular intervals.
A graphical representation of a circuit, using standard symbols to represent each circuit component.
An electric current in one direction only.
The movement of energy within a system. Can include the transformation of one type of energy to
another (with some loss). Relevant examples include electricity to motion (fan), electricity to light and
heat (light bulb), electricity to sound and motion (sound system).
A device or the resistance of a device to which electricity is delivered.
An electric circuit providing more than one conducting path.
A device used to control current in an electric circuit by providing resistance.
An electric circuit providing a single conducting path such that current passes through each
element in turn without branching.
SHPE Foundation
Online SHPE Jr. Member Activities
Light Your Way
Introduction:
• Consider why some electronic games or toys require more
batteries than other games or toys. (Some toys need more
power, some games need more electricity.) Three AA
batteries connected “in series” can provide more voltage
than a single AA battery. Electrical circuits as well as
batteries can be "in series" or ”in parallel”.
• How do electrical engineers know how many batteries are
needed to operate an electronic game or toy? They
create a map of the circuit, or circuit diagram, to
determine the necessary voltage and current to supply
the power the device needs to operate.
SHPE Foundation
Online SHPE Jr. Member Activities
Light Your Way
Introduction:
• Why do some devices use batteries and other devices use
a wall outlet for power? (Batteries produce a different
type of current than a wall outlet.) The current that comes
from a battery is called direct current (DC). The current
that comes from a wall outlet in our homes or schools is
called alternating current (AC).
• Many televisions, computers, DVD players and stereos
have hardware (equipment) inside the device that
converts the alternating current (AC) to direct current
(DC) for operation of the device.
SHPE Foundation
Online SHPE Jr. Member Activities
Light Your Way
Circuit Diagrams:
o Circuit Diagrams are graphical
representations of circuits or electrical
devices; the circuit diagram is the
language of electrical design and
engineering.
o Each component of a circuit has a
corresponding standard symbol.
o In circuit diagrams, symbols are linked
together to show the circuit
construction – the diagram is a map
that anyone can read to learn how to
build the circuit.
o Interpreting circuit diagrams is an
essential skill for electrical engineers
and many other types of engineers.
SHPE Foundation
Online SHPE Jr. Member Activities
Light Your Way
How are Electrical Elements Connected in a Circuit:
o In series - When the parts of a circuit are connected such that there is a
single conducting path between them.
o In parallel – When circuit elements are connected across common
points such that there is more than one conducting path through the
circuit.
o A typical electrical device is composed of many smaller series and
parallel portions.
SHPE Foundation
Online SHPE Jr. Member Activities
Light Your Way
Ohm’s Law and Series Circuits:
o Ohm’s Law is a fundamental mathematical equation describing
the relationship between voltage, current and resistance.
o R = V/I, where R = resistance of a circuit element, V = total
voltage supplied to the circuit by a power source (battery), and
I = current through the circuit.
o V = I*R – Ohm’s Law for predicting a voltage drop across a
circuit element with a known resistance and a known current
passing through.
o The voltage supplied to the circuit, V, and the total voltage
drop throughout the circuit is equal to I*RT = VT, where RT is the
total resistance in the circuit.
SHPE Foundation
Online SHPE Jr. Member Activities
Light Your Way
Ohm’s Law and Series Circuits:
o In the diagram below, there is only one path for charge movement
through the circuit, the current is the same throughout the circuit
o As electrons move through the circuit, their flow is resisted by each light
bulb, such that the total resistance to charge movement is the sum of
all the resistances in the path.
o I = V/R – total current is equal to the voltage divided by the total
resistance.
o There is a voltage drop across each bulb. The sum of the voltage drops
is equal to the voltage of the power source (battery)
o The voltage drop across each light bulb is directly proportional to that
bulb’s resistance (V = I*R)
SHPE Foundation
Online SHPE Jr. Member Activities
Light Your Way
Ohm’s Law and Series Circuits:
o When batteries are linked in series, the total voltage is the sum of the
voltages of each battery.
SHPE Foundation
Online SHPE Jr. Member Activities
Light Your Way
DC v. AC:
o Direct current (DC) is the movement of charge in a circuit in one
direction only. Batteries, photovoltaic cells and some generators
provide direct current (DC).
• In a battery-powered flashlight, electrons leave the negative
terminal of the battery and move through the flashlight circuit to
the positive terminal.
o In alternating current (AC), electrons move back and forth in a circuit.
The electrons only move a small distance around a relatively fixed
position in the circuit.
• AC has been proven to be a more effective way to transmit
electrical power.
• Whenever you plug an electrical device into a wall socket, you are
using AC.
• The current direction alternates because the direction of voltage is
alternated at the power plant. In the US, we use current that
changes direction 60 times a second.
SHPE Foundation
Online SHPE Jr. Member Activities
Light Your Way
Background on the Flashlight:
o The first flashlight was invented in 1896, made possible by the invention
of the D-cell battery.
o Called “flash lights” because they provided a brief flash of light when
the user pushed a switch – unlike the steady light beam produced by
today’s flashlights.
o Over time, the parts of a flashlight haven’t changed much! The
flashlight you will build in this activity has all these parts except for the
protective glass and the spring.
SHPE Foundation
Online SHPE Jr. Member Activities
Light Your Way
Procedure Overview
o Consider the components that make up a typical flashlight, then
design, build, and test your own flashlight.
o Note: if you are using pre-made switches, you will not need to
assemble any switch materials.
The basic circuit for a flashlight
SHPE Foundation
Online SHPE Jr. Member Activities
Light Your Way
Procedure
1. Open-ended design: The goal of this activity is to design and
construct a working flashlight using only the listed materials. The
flashlight must turn on and off using a switch. Also, all of the wiring
and batteries must be contained within the paper towel tubes.
2. Consider the qualities of a good flashlight. (On/off switch, reliable
switch, easy-to-use switch, easy to carry, small size, bright beam of
light, lasts a long time, does not break)
3. Draw a flashlight. (Parts include: case, spring, bulb, switch,
protective glass/plastic, reflector, batteries) Consider the function
of each part of the flashlight that has been drawn.
4. Brainstorm the design of your flashlight, determining which
materials you will use for each part. Document your material
plans.
SHPE Foundation
Online SHPE Jr. Member Activities
Light Your Way
Procedure
5. Draw a circuit diagram for your flashlight. Write out the steps you are
going to take to build your flashlight.
6. With the listed materials, construct your flashlight design.
7. Test your flashlight. To be considered reliable, it should be able to light
up three times in a row. If your flashlight does not work, compare the
flashlight circuit diagram to your flashlight’s circuit.
8. Write down any design changes or fabrication improvements you
need to make, and implement the changes so the flashlight works.
The circuit diagram
SHPE Foundation
Online SHPE Jr. Member Activities
Light Your Way
Safety Issues
o Do not play with the insulated wire
o Do not hold the insulated wires on the D-cell battery with you fingers
for extended periods of time. The stripped ends of the wire heat up
when held on the battery terminals.
Troubleshooting Tips
o Slice small cardboard tubes down the middle to accommodate the
D-cell batteries.
o A paperclip may be used to hold the light bulb in place.
o Make sure all of your connections are reliable, so when you move the
flashlight, the connection doesn’t come loose.
o Ideally, all of the wires used in the flashlight should be contained within
the paper towel tube – no wires should be hanging out. If you have
problems making the switch inside the tube, set up your switch
externally.
SHPE Foundation
Online SHPE Jr. Member Activities
Light Your Way
Sales Pitch!
o Pretend to be a salesperson who are trying to sell your flashlights to
a manufacturer or a consumer. Create a persuasive power or flyer,
as well as a 10-minute sales pitch of your flashlight design for
presenting to a friend or family member. Incorporate into your
sales pitch your series circuit diagram, the parts and the feel of the
flashlight and how it works.
Activity Extension
o Portable flashlights can be powered by means other than
batteries. Conduct Internet research on solar-powered flashlights,
"shake" flashlights and "crank" flashlights. Consider the
environmental and economic implications of using these types of
flashlights.
SHPE Foundation
SHPE Jr. Chapter Curriculum
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o over 1,350 standards-based engineering lessons and activities
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o carleigh.samson@colorado.edu
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