One risk in electrical circuits is a surge in current.
What do we mean by 'surge' and why is it dangerous?
A surge is a sudden increase in current.
This can damage an appliance, cause a fire, or give an electric shock.
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Name 4 safety mechanisms that can be used in electrical circuits.
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How does a fuse work?
Fuses have a thin wire which melts and breaks the circuit when the current is too high.
The rating of a fuse is the current that will cause the fuse to break the circuit.
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How do you decide which fuse rating to use for a given electrical circuit?
Generally you should use a fuse with a rating a few amps above the recommended current for the appliance.
Using a fuse with a rating a few amps above the recommended current means that it won't break under normal use. However, if there is a surge and the current rises significantly then it will surpass the rating and break the fuse.
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How do circuit breakers work?
Circuit breakers act like a switch that will trip (open) when there is a surge in current.
They can be reset electrically, rather than having to be replaced.
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How do earth wires protect us from electric shocks?
The earth wire is connected to the casing of the appliance. If the live wire touches the appliance casing, the earth wire provides an alternative pathway for electricity to flow.
This means we can't get an electric shock from touching the live appliance casing.
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How does double insulation work?
Double insulation is where an appliance is covered in a layer of plastic.
As plastic doesn't conduct electricity, we can't get an electric shock from touching it, even if the appliance is live.
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