12th Dec '25

Switches & Capacitors

Switches

Switches control devices in simple , for example:

A circuit to control a single light in a room

A circuit with two switches to control one light

A circuit to independently control two lights with two switches

A circuit to control a light that requires two switches to be closed at once

We can also use electromagnetically activated switches called . This allows a control current to activate a load current, capable of doing work.

When the switch is , the flows in the 'control' (red) circuit. The coil becomes an attracting the which pushes the together. This completes the other (blue) circuit activating a device, in this case a

Capacitors

Capacitors consist of two close, conductive , separated by an (could be an air gap).

When there is a potential difference applied across the plates, extra begins to fill up on one plate and charge from the other. This creates a potential difference between the plates as more and more charge is forced on.

This all takes time and so a capacitor can be used as simple timers in electronic circuits and can be used as an 'input sensor' for a time delay switch.