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Electrical conductors, semi-conductors and insulators

Definition 1: Electrical conductor

An electrical conductor is a substance that allows an electrical current to pass through it.

Electrical conductors are usually metals. Copper is one of the best electrical conductors, and this is why it is used to make conducting wire. In reality, silver actually has an even higher electrical conductivity than copper, but silver is too expensive to use.

Conductors and insulators

In the overhead power lines that we see above us, aluminium is used. The aluminium usually surrounds a steel core which adds makes it stronger so that it doesn't break when it is stretched across distances. Sometimes gold is used to make wire because it is very resistant to surface corrosion. Corrosion is when a material starts to deteriorate because of its reactions with oxygen and water in the air.

Power lines

Image

Picture by motumboe on Flickr.com

Definition 2: Insulators

An insulator is a non-conducting material that does not carry any charge.

Examples of insulators are plastic and wood. Semi-conductors behave like insulators when they are cold, and like conductors when they are hot. The elements silicon and germanium are examples of semi-conductors.

General experiment 1: Electrical conductivity

Aim

To investigate the electrical conductivity of a number of substances

Apparatus

  • two or three cells

  • light bulb

  • crocodile clips

  • wire leads

  • a selection of test substances (e.g. a piece of plastic, aluminium can, metal pencil sharpener, magnet, wood, chalk, cloth).

Figure 1
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Method

  1. Set up the circuit as shown above, so that the test substance is held between the two crocodile clips. The wire leads should be connected to the cells and the light bulb should also be connected into the circuit.

  2. Place the test substances one by one between the crocodile clips and see what happens to the light bulb. If the light bulb shines it means that current is flowing and the substance you are testing is an electrical conductor.

Results

Record your results in the table below:

Table 1

Test substance

Metal/non-metal

Does the light bulb glow?

Conductor or insulator

       
       
       
       

Conclusions

In the substances that were tested, the metals were able to conduct electricity and the non-metals were not. Metals are good electrical conductors and non-metals are not.

Circuit Construction Kit (DC Only)
Click to Run

This simulation allows you to work through the above activity. For this simulation use the grab bag option to get materials to test. Set up the circuit as described in the activity.