Electric charge

Some particles carry an electric charge. In electric wires these particles are electrons. We get an electric current when these charged particles move from place to place.

Electric current

An electric current is a flow of charge, and in a wire this will be a flow of electrons. We need two things for an electric current to flow:

  1. something to transfer energy to the electrons, such as a battery or power pack
  2. a complete path for the electrons to flow through (an electric circuit)

Electric circuits

The simplest complete circuit is a piece of wire from one end of a battery to the other. An electric current can flow in the wire from one end of the battery to the other, but nothing useful happens. The wire just gets very hot and the battery loses stored internal energy – it ‘goes flat’ and stops working.

To do something useful with the electric current, you need to put an electrical component into the circuit (such as a lamp), that can use the current in a useful way.

Three circuits: the first is incomplete - the wire isn't connected to the lamp on one side; the second is incomplete - the battery is missing; the third is complete and the lamp lights upThe lamp will only light up if there is a complete circuit with a battery

You usually add a switch to the circuit. This lets you break the circuit and stop the electric current when you want to.