Components in a simple circuit

Power supply:

A battery is an example of a power supply. This is the source of electrical potential energy that will push electric charges around a circuit.

A load (resistance):

This is the electrical device like a light bulb where the electrical energy is converted into another form of energy. For example light bulbs convert electrical energy into light and heat.

Conducting leads:

Metal wires allow the electrical energy to travel through them because they are conductors of electricity.

Switch:

A switch opens and closes the circuit. For the electric current to flow, the circuit must be closed (complete).