Basic Switches

This lab deals with how to properly connect an switch to a circuit.

First, two vocabulary:

• When two components are in series, they adjacent, so all current through one component goes through the other.
• When two components are in parallel, they are in a series circuit, one after the other.

Materials

• A battery
• A light bulb
• A switch. When you are first learning to use a switch, its good to use a throw switch.
• Several alligator clip wires

Procedure and Questions

Note: All of the switches in the circuit diagrams for this lab are being drawn as open switch. This is because it is much easier to see them. Obviously, the point is to open and close the switch after you build it to see how it works.

1. Start with a circuit containing just a light bulb and a battery:
   
   
   Then, add a switch in series with the light bulb, like this:
   
   Move the switch up and down. Does it work?
2. If you have an old-school throw-switch, do you need to close it all the way to get the light bulb to turn on? How much do you need to close it? Why?
3. Now try rewiring your circuit so that the switch is connected to the light bulb in parallel:
   
   Try flipping the switch on and off. It should still work, turning the light bulb turn on and off.....but you will notice something a little strange. What?
4. I like to call this a "reverse switch." Why does that name fit?
5. Turn the switch in parallel "on." The light bulbs should now be off. Is there current running? Wait for a little bit, and see if the battery gets warm.
6. Look back at the previous lab on short circuits. Why is the light bulb off when the switch is on? Why is the light bulb on when the battery is off?
7. If you want a switch to properly control a light bulb, do yo want to connect it in series or parallel with the light bulb? Give two reasons why: one reason that deals with safety and another with making your circuit easy to understand.

Coming soon: picture of a throw switch