Some materials are good electrical conductors: we can use them to complete a circuit. Some materials do not conduct at all. Objects that can be used as wires are called electrical conductors.

Choose a set of 10 objects to test. Among the objects you could include a light bulb, a buzzer, plain water, some very salty or vinegary water, a pencil lead, and one of your fingers (it won't hurt.... much). Include something that you think is a good conductor and something that you think does not conduct at all.

Build this circuit, using two batteries in series, and then fill the gap with one of the objects, to see if it completes the circuit. If the light bulb lights, we will call the object a good conductor. If the light bulb only glows dimly, we will call it a poor conductor. If nothing happens, it is a very poor conductor, or perhaps an insulator. Test each of the objects you have chosen, and enter the results in the table.

Build another circuit by replacing the light bulb by a buzzer, and test the objects again. You will see that some of the objects that gave no response with a light bulb make a tiny sound with the buzzer, while some still do nothing. Enter these results in your table, too.

Finally build a third circuit using a light- emitting diode, and test the objects a third time.
Conductors and insulators

object	circuit 1 (light bulb)	circuit 2 (buzzer)	circuit 3 (LED)

Most objects can be classified as being conductors or insulators; however, this depends somewhat on the sensitivity of the test, since everything conducts a little bit. There are also objects like the light-emitting diode, that do not conduct at all when 1.5 V is applied, but become (poor) conductors when 3 volts are applied.