Grade 4 · Unit 5: Electricity and magnetism

Circuits with buzzers

Make a sound – and build an alarm.

A buzzer component has a red wire and a black wire.

Buzzers make sound

A buzzer makes a sound when current flows through it. Inside, a thin disc vibrates very fast. Buzzers are used in doorbells, timers and microwaves.

Buzzers are used in microwaves, washing machines and reversing lorries to give a warning or tell us something is finished.

Which way round?

Many buzzers work only one way round. This is called polarity. The red wire joins to the + end of the cell, the black wire to the – end. If a buzzer is silent, try turning it round.

LEDs also only work one way round. If an LED does not light, try turning it round.

Making an alarm

An alarm uses a switch and a buzzer. A pressure switch under a mat closes when someone stands on it. The buzzer sounds! A door alarm can close a circuit when the door opens.

Shops use door alarms that buzz when a customer comes in, so the shopkeeper knows even if they are in the back room.

Alarms that save lives

Smoke alarms beep when they detect smoke. They give people time to get out of a building safely.

Smoke alarms should be tested once a month by pressing their test button. Their batteries need changing about once a year.

What I learnt