This conductivity experiment is an excellent science project for a homeschool program in which students are learning about electricity and what factors make electricity work. As with any truly memorable hands-on homeschool program, students will be able to make their own conductivity tester that they can use to test for electric currents!

To get started with this project, students should learn a little more about the background so they understand why this project is important (and what they are actually learning).

Background
First, students should learn that water alone is not a great conductor of electricity. However, when some substances are put into the water, the water can become an excellent source of conductivity. In this experiment, students will learn which solutions make the best electricity conductors when combined with water by using a simple light bulb; the brighter the light bulb glows, the better the electric current is through the water.

    •    12-volt AC adapter
    •    Audio cable with a ¼ or 1/8 inch monaural plug at one end
    •    12-volt flashlight bulb with socket
    •    A 4x4x1 block of wood
    •    2 1-inch screws
    •    1 ¾-inch round-head screw with a washer
    •    Wire cutter and stripper
    •    Screw driver

Once you have these materials gathered together, you’re ready to get started.

Steps
    •    Cut the AC adapter plug. Separate the cord by about 4 inches so that you have two separate conductors. Remove about one inch of the insulation from these cords.
    •    Cut the audio cable cord approximately 2 feet from the plug and remove about 4 inches of the insulation. Unwrap the wires from the insulation and twist them together. Remove about one inch of the insulation from the middle wire.
    •    Using your wood screws, screw the light bulb socket into the wood block. Place the washer and round-headed screw about half an inch from the socket, but do not tighten the screw. This is one homeschool program science experiment where you’ll get to do some construction work! By the way, if you teach science at home, a great resource is the free Homeschool Science Experiment Guide and workbook.
    •    Take one of the AC adapter wires and wrap it around the round-headed screw – above the washer. Do the same with the twisted wire from the audio plug. Tighten the screw.
    •    Take the other stripped wires from the AC adapter and audio plug and wrap them around separate terminals of the light bulb socket.
    •    Screw the 12-volt bulb into the light bulb socket.
    •    You have now made a conductivity tester! To test it, simply plug the AC adapter into a wall outlet. You’ll notice that the light bulb will not illuminate. However, if you touch the audio plug to a metal object, the light will illuminate. When the light illuminates, current is flowing through the metal.
    •    To test the conductivity of different solutions, simply add different materials to a glass of water. You’ll notice that distilled water will not make your bulb glow. However, tap water may make your bulb glow dimly. Salt water may make your bulb grow brightly.
    •    Record your observations.

After completing this project, make sure that you review your notes and observations so that you get a good idea of what solutions created conductivity and which did not. Now’s the time to learn more about electrons, subatomic particles, and the electrical charges that make them all work together! Do your own research on why and how electricity works or skip to the next chapter in your science book!