Conductors and insulators

A conductor is an object that electricity can pass through. An insulator is an object that electricity can pass through. Metals are good conductors. Wood, plastic, glass and rubber are all electrical insulators.

Conductors

Insulators

Testing an insulator

Electricity can only travel round a complete circuit of conducting components. If the material that you're testing is an insulator, the bulb won't light up because electricity can't flow round the circuit.

Testing a conductor

If the material you are testing is a conductor, it will complete the circuit. Electricity will flow round the circuit and the bulb will light up.