Use electrical tape to attach two batteries together, with their poles facing in opposite directions. The bump at the bottom of the battery is the positive pole. The flat end of the battery is the negative pole. Tape a paper clip between the negative and positive poles of your batteries. Cut two pieces of number 22 insulated copper wire and strip about one-half inch of insulation off each end. Use electrical tape to connect one stripped end of one wire to the other negative end of the battery. Repeat that process with your second wire and the positive pole. The metal in the paper clip acts as a conductor between your two batteries and the wires are now ready to power other projects.
To build your switch, take one thumbtack and hook a paper clip around the back of the tack. Wind one stripped end of a 10-inch piece of number 22 insulated copper wire around the base of the tack and attach it to a wood block. Wind a second wire around another tack and attach it to the block of wood; connect the wire from the positive end of your battery pack to this wire. Place a paper clip on the back of a third thumbtack and press it into the middle of your block between the two other wires. Nail a clothespin to a second wood block. Tack a loose wire from your switch directly below the clothespin. Now wrap the end of the remaining unconnected wire around the base of the bulb and clamp it in the clothespin to connect the circuit. Use a thumbtack to connect the other end of the wire to the block of wood. To connect your circuit, take the other stripped end of the wire that you connected to the bulb and connect it to the positive wire on the battery pack from your first project. Attach the end of the second wire that you attached to the wood block to the negative wire on your battery pack. Press down on the paper clip that you attached to the wooden block. The paper clip connects the circuit, allowing electricity to flow through and light up the bulb.
Use the circuit switch to determine the conductivity of different materials. Collect a variety of objects that you want to test. Detach the negative ends of the wires that you connected to the circuit switch. Attach the two ends of those wires to opposite ends of any object that you want to test. If the object conducts electricity, the bulb will light up when you press your switch. Pay attention to which materials cause the bulb to light up strongly, more dimly or not at all and chart your results.