Component guide
How to Use the Switch
- Grades 3-8
- 10 minute activity
- NGSS 4-PS3-2
Quick answer
A switch opens and closes a circuit. When it is on (1), the circuit is a closed loop and electricity flows. When it is off (0), the switch makes a gap and everything in that loop stops. To add a switch to a play dough circuit, place it so electricity has to pass through it to reach the LED.
What does a switch do?
A switch is a gate in a circuit. Close the gate and electricity can flow all the way around the loop. Open it and the loop is broken, so the electricity stops.
You use switches all day: light switches, power buttons, the trigger on a flashlight. Many switches are marked with 1 for on and 0 for off. The power symbol on your devices is a 1 and a 0 combined.
Try it with dough
Add a switch to your dough circuit
You need
- Battery holder with 4 AA batteries
- Conductive (salty) play dough
- 1 LED
- 1 switch
Steps
- Make three pieces of conductive dough and line them up with a gap between each piece.
- Push the red battery wire into the first piece and the black wire into the third piece.
- Put the LED across the first gap: long leg in the first piece, short leg in the middle piece.
- Put the switch across the second gap: one switch wire in the middle piece and the other in the third piece.
- Switch the battery holder on, then flip your switch between 1 and 0.
What happens
At 1, the LED lights because the switch closes the loop. At 0, the switch opens a gap and the LED goes dark.
Not working?
- LED always on? The middle and last pieces of dough may be touching, which lets electricity go around the switch.
- LED never on? Check the LED direction and the batteries, and make sure the switch wires are pushed in deeply.
Where does the switch go?
Anywhere in the loop, as long as electricity has to go through it. A switch before the LED or after the LED works the same way, because opening the loop anywhere stops the flow everywhere.
A switch also has no polarity, so its two wires can go either way around. If you put a switch before several LEDs that branch off in parallel, one switch controls them all.
Switch ideas to try
- A flashlight you can turn on and off.
- A nightlight with a glowing moon or star.
- An alarm with a switch, an LED and a buzzer.
- A fan with an on and off switch for the motor.
Key words
- Switch
- A part that opens and closes a circuit.
- Closed circuit
- A complete loop. With the switch on, electricity flows.
- Open circuit
- A loop with a gap. With the switch off, electricity stops.
- 1 and 0
- The marks for on (1) and off (0) on many switches.
- Polarity
- Having a positive and a negative side. Switches do not have polarity.
Watch: how to use the switch
Switch questions
What do 1 and 0 mean on a switch?
1 means on: the switch closes the circuit and electricity flows. 0 means off: the switch opens the circuit and electricity stops.
Does a switch have polarity?
No. A switch only opens and closes the loop, so its wires can go either way around.
Where should the switch go in a circuit?
Anywhere in the loop where electricity has to pass through it. Before or after the LED both work, because opening the loop anywhere stops the flow everywhere in that loop.
Why does my LED stay on when the switch is off?
Electricity is finding a way around the switch, usually because the two pieces of dough the switch connects are touching. Pull them apart or put white insulating dough between them.
What is the difference between an open circuit and a closed circuit?
A closed circuit is a complete loop, so electricity flows. An open circuit has a gap, so electricity stops. A switch lets you choose between the two.
Can one switch control several LEDs?
Yes. Put the switch in the part of the loop that all the electricity has to pass through, before the LEDs branch off, and it turns them all on and off together.
Printable guide: Components Explained (PDF)
Next, try a project
Build the light-up Reindeer Flip the switch and the nose glows.