When you turn on a switch, it’s difficult to really see what’s going on… which is why we make our own from paperclips, brass fasteners, and index cards.
Kids can see the circuit on both sides of the card, so it makes sense why it works (especially after doing ‘Conductivity Testers’).
SPST stands for Single Pole, Single Throw, which means that the switch turns on only one circuit at a time. This is a great switch for one of the robots we’ll be making soon, as it only needs one motor to turn on and off.
[am4show have=’p8;p9;p20;p47;p106;p108;p97;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]
Think of this switch like a train track. When you throw the switches one way, the train (electrons) can race around the track at top speed. When you turn the switch to the OFF position, it’s like a bridge collapse for the train – there’s no way for the electrons to jump across from the brass fastener to the paper clip. When you switch it to the ON position (both sides), you’ve rebuilt the bridges for the train (electrons).
Troubleshooting: The two tabs on the back of the motor are the places to clip in the power from the battery pack. Since these motors spin quickly and the shaft is tiny, add a piece of tape to the shaft to see the spinning action more clearly.
Kids can make their own switches so they can trace the path the electricity takes with a finger. See what you think about this SPST:
Here’s what you need:
- 2 AA batteries
- AA battery case
- 3 alligator wires
- index card
- 2 brass fasteners
- paper clips
- buzzer, motor, or LED
Download Student Worksheet & Exercises
Exercises
- If you want to reverse the spin direction of a motor without using a switch, what can you do?
- A simple switch can be made out of what kinds of materials?
- How would you make your SPST switch an NC (normally closed) switch?
- How did you have to connect your circuit in order for both the LED and motor to work at the same time? Draw it here:
- Draw a picture of your experiment that explains how the SPST switch works, and show how electricity flows through your circuit:
Extra Credit (for students who have completed Part 3):
- Draw a picture of your experiment that explains how the DPDT switch works in your circuit and show how to wire up the circuit.
[/am4show]
No, thumbtacks won’t really do the job. Thumbtacks can’t hold on to paper like brass fasteners can. Also, some thumbtacks have a plastic coating, which will prevent them from conducting electricity. So, please be sure to use brass thumbtacks.
Can I use thumbtacks instead of brass fasteners?
Sofia, age 10