Conductors and insulators
In this topic you will:
- discover the difference between electrical conductors and insulators
- learn about uses for conductors and insulators
- test some materials for electrical conduction or insulation.
Key words
- allow current to flow
- conduct
- electricity
- conductor
- inhibit
- insulator
Conductors
Conductors are materials that conduct electricity.
That means conductors allow current to flow. Electric current can flow through a conductor.
You saw in Topic 9.1 that electrons move when current flows.
Therefore, a conductor is a material in which electrons are free to move. Conductors allow electrons to flow.
All metals are conductors.
Wires that carry electric current are made from metal.
Most wires in houses and schools are made from copper, with a plastic coating.
Wires that cover long distances are usually made from aluminium or steel. These metals are cheaper than copper.
Some circuits, such as those in phones and laptops, do not use wires. The printed circuit board in the bottom right picture has copper tracks instead of wires. The tracks are green because the copper is coated with another material.
Common Mistake
Not all materials that carry electricity are visible wires — in many devices, copper tracks on a circuit board replace traditional wires. Students often forget that conductors don't always look like wires!
Insulators
Electrical insulators are materials that do not allow current to flow through.
Most non-metals, such as plastic, wood, air and cotton, are insulators.
In an insulator, the electrons are not free to move.
Because the electrons are not free to move, current cannot flow. Insulators inhibit electron flow.
Insulators are used to keep people safe from electricity.
The plug in the picture below is made from plastic so people can touch the plug. The wire coming from the plug is also coated in plastic to protect people from electric shocks.
Plastic insulation on wires is also useful because the plastic can be coloured differently to identify each wire.
The insulators on these power lines stop the current from flowing from the wires into the metal pylon. If the current flowed to the pylon, electrical energy would be dissipated into the ground. Also, people and animals touching the pylon would get electric shocks.
Important Concept
Insulators protect people by preventing the flow of electricity. They are essential in tools, wires, and large-scale power systems to reduce the risk of shocks and energy loss.
Questions
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Examples of electrical conductors include steel and aluminium.
Examples of electrical insulators include plastic and wood.
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Silver is much more expensive than copper, so it would be too costly to use for home wiring despite its better conductivity.
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Plastic is an electrical insulator, so it prevents electric shocks when people handle the plug.
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Metal is a good conductor of electricity and allows current to flow from the plug to the device.
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In conductors, electrons are free to move, allowing current to flow. In insulators, electrons are not free to move, so current cannot flow.
Think Like a Scientist
In this task, you will test some materials to find out whether they are conductors or insulators.
You will need:
- a battery or cell
- a lamp
- crocodile clips
- wires
- a selection of materials to test (e.g., items found in the classroom)
Steps
- Set up a circuit as shown in the drawing.
- Touch the crocodile clips together and watch what happens to the lamp.
- Test some materials by connecting the materials between the crocodile clips.
Follow-Up Questions
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To check that the circuit is working properly and that the lamp lights up when there is a complete circuit.
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If the material allows current to flow and the lamp lights up, it is a conductor. If the lamp does not light up, the material is an insulator.
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Use a table listing each material and whether the lamp lit up. Include a column for conclusion: conductor or insulator.
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Most metals are conductors; plastics, wood, and fabric are usually insulators. Shiny and metallic objects tend to conduct electricity.
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The metal might be coated with paint, plastic, or rust, preventing a good electrical contact during the test.
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Scratch or sand the surface to remove coatings and ensure metal is exposed before retesting with the crocodile clips.