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Science

Safe electricals

An electric current is a flow of electric charge. Most mains-powered appliances need three wires to work safely: live, neutral and earth.

Resistance (measured in ohms) is a measure of how hard it is for a current to flow through a circuit component. The size of the current flowing depends on the potential difference (voltage) driving it and the amount of resistance it has to flow through.

Current

Electric current is a flow of electric charge. No current can flow if the circuit is broken, for example, when a switch is open. Click on the animation to see what happens to the charges when the switch is opened or closed.

Two things are important for a circuit to work:

  • There must be a complete circuit
  • There must be no short circuits

To check for a complete circuit, follow a wire coming out of the battery with your finger. You should be able to go out of the battery, through the lamp and back to the battery.

To check for a short circuit, see if you can find a way past the lamp without going through any other component. If you can, there is a short circuit and the lamp will not light.

Work out which of these four lamps will light when the switch is closed. Move your mouse over a circuit, then left click to check your answer.

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