A rheostat is a small device that allows you to control voltage flow by using a knob or a dial.

Items you will need:

1. One (1) dry cell lantern battery or Two (2) “D” cell batteries.

2. A 2-inch long piece of wire

3. A socket and a bulb from a flashlight.

4. Roughly 16 inches of wire.

5. One pair of wire cutters.

6. A very long spring. This may be acquired from anywhere. A roll-up window shade has a spring inside the wooden portion. Ask a parent or adult to help.

Directions:

1. When connecting the two batteries, connect them so that the negative pole of one battery is connected to the positive pole of the opposite battery.

2. Using the 16-inch wire, cut it in half with your wire cutters. Attach one piece to each open end of the joined batteries.

3. Using the light socket, connect one end of the wire to the terminal of the light socket and one end of the wire to one end of the spring.

4. Using the 2-inch wire, connect it to the other terminal of the light’s socket.

5. Taking the end of each wire, connect them. Pay attention to how brightly the bulb begins to glow.

6. Taking the short wire, slowly move it down the length of the spring.

What happens?

Discovery:
Because the steel wire of the spring is not a great conductor of electricity, you will find that the further away you move the wire, the dimmer the light becomes. The more wire that the electricity is forced to move through the more resistance. Thus, you have less electricity. Congratulations, you have just created a rheostat! This device is used to calculate and vary the amount of current.

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