Experiment 8

A Light-Bulb Indicator

Materials: 2 long thin nails. 2’ of hookup wire. Bulb socket from Experiment 2. Screw-type flashlight bulb. Flashlight battery. Some tape.

We mentioned that the electric light bulb is a simple device. Well in addition, it operates in the simplest of circuits. An example is the light-bulb indicator you are about to put together.

ASSEMBLING THE INDICATOR. Actually there’s not much to assemble, as you can see.

All you do is hook the light bulb and battery in series and attach the circuit ends to the nails. Make all connections by soldering. But if you have no soldering equipment, use tape. Also cover the nails and nail connections with tape, leaving only the tips exposed.

     WHAT DO WE DO WITH IT? Lots of things. For example you can use it in science experiments to learn whether or not different materials and liquids are good conductors of electricity.

     You can also use it to check items like flashlight bulbs or glass-tube fuses, as shown. Some of these fuses have wires so thin you can hardly see them. If you touched the indicator nails to the ends of such a fuse and the bulb lit up, you’d know the fuse is OK.

     But whatever you do, never use it on anything that is connected to a voltage source (but then you don’t need to be told not to stick your finger in a beehive, do you?).