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Fuses

L.O.:

What do we use fuses and circuit breakers for?

How to use the correct fuse

FuseFuseFuseFuse

Fuse

1. A fault in an appliance can cause the current to be too great and can lead to the wire overheating and possibly causing a fire.

2. A fuse is designed to melt if the current through a circuit is too high, thereby breaking the circuit

3. The fuse should be just higher than the normal working current

4. A circuit breaker can be reset rather than replaced

Fuses & Circuit BreakersFuses & Circuit BreakersFuses & Circuit BreakersFuses & Circuit Breakers

Fuses & Circuit Breakers

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Fuses

1. If an appliance has a metal case it needs to be earthed.

2. A fault could cause the live wire to touch the metal case. If the appliance is earthed a large current flows down the earth wire and melts the fuse. If the appliance was not earthed there would be a risk of electrocution.

Earth wireEarth wireEarth wireEarth wire

Earth wire

Earth wireEarth wireEarth wireEarth wire

Earth wire

An electrical fault (1)An electrical fault (1)An electrical fault (1)An electrical fault (1)

An electrical fault (1)

An electrical fault (2)An electrical fault (2)An electrical fault (2)An electrical fault (2)

An electrical fault (2)

Fuses in plugs are made in standard ratings.

The most common are 3A, 5A and 13A. The fuse should be rated at a slightly higher current than the device needs

• if the device works at 3A, use a 5A fuse • if the device works at 10A, use a 13A fuse

A circuit breaker is an electromagnetic switch that opens and cuts the current off if too much current passes through it.

For the following devices choose fuses from 3A, 5A and 13A.

Operating Current

Fuse

2.1A

11.2A

4.7A

6.0A

4.5A

8.2A

3.0A

13.0A

5.0A

13.0A

5.0A13.0A

Fuses II

Workbook page 93

Fuses

L.O.:

What do we use fuses and circuit breakers for?

How to use the correct fuse