Electrical conductors and insulators revision notes

Edexcel International GCSE Physics (4PH1), chapter 9: Electric charge, specification point 2.22P, 2.16. Free lesson.

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Conductors let electric charge flow, while insulators stop it. Their different behaviour comes from whether electrons can move, which is why cables and plugs use both types of material.

How conductors let charge flow

A conductor is a material that lets electric charge flow through it easily. Metals conduct because some of their electrons are not tied to one atom. These free electrons can move through the whole metal. A current in a metal wire is a flow of negatively charged electrons. Metals such as copper, aluminium and steel conduct. Graphite also conducts. It is a common non-metal that conducts.

How insulators behave differently

In an insulator, electrons are held in place in their atoms, so charge cannot flow through the material. This means charge behaves differently after rubbing: it can move away through a conductor, but stays on the rubbed patch of an insulator. Common insulators include plastics, rubber, glass and dry wood. A conductor held in your hand loses charge because electrons flow through the material and your body.

Why cables and plugs use both materials

Electrical equipment puts conductors where current needs to travel and insulators where people need protection. The material used for each part matches its job. Copper wires carry current because copper is a good conductor with free electrons. Plastic wire coating is an insulator. It stops current reaching you and helps prevent wires touching each other and causing a short circuit. Brass plug pins conduct current into the socket. The hard plastic plug case is safe to hold while the pins are live.

What happens to charge on a metal rod

A metal can carry charge, so it is not true that metals cannot be charged. However, if you hold a charged metal rod, electrons can flow through the metal and through your body, so the charge does not stay on the rod. If the rod is on an insulating handle, the charge stays on it because the handle stops charge flowing away.

Explaining the materials in a cable

For a question about a cable with copper wires covered in plastic, link each material's properties to its job. This explains both how current travels and how the coating protects you.