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/battery-and-bulb-activity/) you made electric circuits from flashlight bulbs and flashlight batteries. In the Grounding and Protection activity (http://theselsproject.org/grounding-and-protection-activity/) 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.
28-gauge wire (small wire) is sufficient for this activity. It is not necessary to use 12- or 14-gauge (large wire) house wire.
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 light-bulb 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 3-way 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.
Next Generation Science Standards
Scientific and Engineering Practices:
– Planning and carrying out investigations
– Constructing explanations and designing solutions
– Energy and matter: Flows, cycles, and conservation
- Using your knowledge of the operation of a circuit breaker panel (see Circuit Breaker Panel (http://theselsproject.org/circuit-breaker-panel-activity/) 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.
- 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.
- 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?
- 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?