Lamps in series. Lamps in parallel. Switches in series. Switches in parallel

Lamps in series

If several lamps are connected in series they will all be switched on and off together by a switch connected anywhere in the circuit. The supply voltage is divided equally between the

lamps (if they are all identical). If one lamp blows, all the lamps will go out because the circuit is broken.

Lamps in parallel

If several lamps are connected in parallel each one has the full supply voltage across it. The lamps may be switched on and off independently by connecting a switch in series with each lamp as shown in the circuit diagram. This arrangement is

used to control the lamps in buildings. This type of circuit is often called a parallel circuit but the switches are in series with the lamps, and it is these switch and lamp pairs that are connected in parallel.

Switches in series

If several on-off switches are connected in series they must all be closed (on) to complete the circuit.

The diagram shows a simple circuit with two switches connected in series to control a lamp. Switch S1 and switch S2 must be closed to light the lamp.

Switches in parallel

If several on-off switches are connected in parallel only one needs to be closed (on) to complete the circuit.

The diagram shows a simple circuit with two switches connected in parallel to control a lamp. Switch S1 or switch S2 (or both of them) must be closed to light the lamp.