Grade 4 · Unit 5: Electricity and magnetism

Switches

Open the switch, break the circuit.

Controlling a circuit

A switch lets us turn a circuit on and off. When the switch is closed, the circuit is complete and current flows. When it is open, there is a gap and current stops.

A switch is just a gap that we can open and close safely, without touching the electricity.

Kinds of switches

Some switches are pressed, like a doorbell. Some are slid, like a torch switch. Some rock up and down, like a wall switch. All of them open and close a gap.

Light-sensitive switches turn street lights on when it gets dark, and timer switches turn things on at set times.

Make your own switch

A paper clip and two drawing pins can make a switch. The paper clip is a metal conductor. When it touches both pins, the circuit is closed.

A pressure switch closes when you stand on it. Burglar alarms use them under doormats.

Where to put the switch

In a simple loop, a switch can go anywhere in the circuit. Wherever it is, opening it breaks the whole loop.

In a house, each room has its own switches and loops, so turning off one light does not turn off the whole house.

What I learnt

• I know that switches open and close a gap in a circuit.
• I can make and test a simple switch.