HOUSEHOLD ELECTRIC CIRCUITS ACTIVITY (PART 1)
Construction Context
In this activity you will explore what it means to wire circuit for a light and a switch using
household circuit materials. In the Battery and Bulb activity
(http://theselsproject.org/battery­and­bulb­activity/) you made electric circuits from
flashlight bulbs and flashlight batteries. In the Grounding and Protection activity
(http://theselsproject.org/grounding­and­protection­activity/) you explored how a
battery and bulb can be used to examine the
electrical grounding in your home by seeing how
metal parts of appliances or conduit are connected
to ground for your protection. This activity takes the
next step in making science knowledge useful in
everyday living.
Our common everyday experience with electricity is
through switches or outlets whose inside structure
we cannot see. We can’t even see the wiring to and from the switch because under normal
circumstances it is unsafe to have this wiring exposed. In this activity, the wiring will be
exposed and we will connect to house current. Someone who understands
house wiring and household electrical power should be carefully supervising this
activity,
Household power is alternating current (AC) and 120 volts. See the video on this site
about Electrical Generation. In science class, you learn about the relationship between
voltage, current and resistance as V = I x R. House power keeps the voltage constant at
120V and the current changes related to the resistance of the appliance or I = V/R.
Even though this activity makes the wiring visible, it does not make the inside structure
household electrical components visible. This you will have to figure out for yourself. To do
that it will be necessary for you to have a battery and bulb and wires handy. The knowledge
you are building about circuits will be necessary for figuring out how switches and outlets
work. Of course the Internet can be helpful here, but it cannot replace physically testing the
connections on the device.
One reason for learning about electricity in school science or technology classes is
because these ideas are directly useful in your life now! Understanding how electricity is
generated, distributed, and used inside a home, school, or work can be of great benefit to
you now! This knowledge can keep you safe, keep things working, and perhaps be
knowledge useful in a job, earning you more money.
Materials
28­gauge wire (small wire) is sufficient for this activity. It is not necessary to use 12­ or
14­gauge (large wire) house wire.
Activity Description
1. Visit web pages (e.g. http://howthingswork.org) explaining how switches, outlets, fixtures
work
2. If you don’t have the parts around your house or classroom you will need to go buy some
household electrical supplies.
You will need:
* one switch (at large chain stores you can get cheap ones for under $1)
* one outlet (the things you plug cords into) (under $2)
* one light­bulb fixture (cheap white ceramic ones should be under $4)
* one garbage disposal cord (plug at one end and bare wires at the other)
* some wire
* two 3­way light switches (the cheapest are under $3 each)
3. Warning: You will be working with 120V household current. You should always
do this with another person in the room who knows how to turn off the breaker if
something goes wrong. Read through all instructions before starting. You will need
to have the light switch turn on and off the light, but have the outlet “on” all the time (the
switch should not turn it on or off). Make your circuit without having anything plugged into the
wall. After you have made your circuit, take the exposed wires of the garbage disposal
cord and attaching them to your circuit. Warning: the garbage disposal cord should
not be plugged in while you are making your circuit or touching any exposed
wires. Once you have finished making your circuit, plug a lamp into the outlet in your circuit
so that you will be able to check if it works. When this is done, plug your garbage disposal
cord into the wall to show that your circuit works as intended.Warning: If anything
sparks, or if your circuit breakers throws (the power goes out in part or all of the
house), immediately unplug the disposal cord, and contact someone who
understands the circuit before attempting this again. Reset your breaker when you
know things are safe.
4. You will find more challenges and learn more about the wiring in your house in the activity
Household Electric Circuits II.
Science Concepts
Distribution
Next Generation Science Standards
Scientific and Engineering Practices
­ Planning and carrying out investigations
­ Constructing explanations and designing solutions
Crosscutting Concepts
­ Energy and matter: Flows, cycles, and conservation
Discussion Questions
1. Using your knowledge of the operation of a circuit breaker panel (see Circuit
Breaker Panel (http://theselsproject.org/circuit­breaker­panel­activity/) see if
you can trace where the wires would go in the ceiling, walls, and crawl space or
basement of your house to wire a light in the kitchen. In a bedroom. For the outlets
in the living room.
2. Make a drawing of the house and lay out the wiring for all of the electrical
connections in one room. Using your knowledge of the circuit breaker panel,
determine how many different circuits are in the room you are studying. Revise your
diagram to show which outlets and which lights are on each circuit.
3. Once you’ve determined how many outlets are on a particular circuit, find out how
much current the circuit breaker protecting that circuit will handle before “tripping”.
Look at the number on the end of the circuit breaker switch. It usually says 15 amps.
Which appliances would you need to be careful not to plug into that one circuit at the
same time?
4. If you have access to a Vernier Watt’s Up meter, you can determine how much
power different appliances use, for example a vacuum cleaner, a computer, 150
watt lamp, or TV. Which ones use the most energy? Which the least? Why? See
the graph of computer power usage using Watt’s Up connected to a computer
display. What do you think caused the spikes in energy use in the computer? What
goes on and off as you are using a computer?