Fuses & Earthing
This lesson covers:
- The 4 main safety mechanisms that are used in electrical circuits:
- Fuses and circuit breakers, which prevent damage due to a surge in current
- Earthing and double insulation, which minimise electric shocks
resistance / fire / voltage / current
One risk in electric circuits is a surge in current. The sudden increase in can damage the appliance, cause a , or give an electric shock.
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Which of the following safety features are used to protect against surges in current?
(Select all that apply)
Fuses
Circuit breakers
Earth wires
Double insulation
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rating / high / low / description
Fuses have a thin wire which melts and breaks the circuit when the current is too .
The of a fuse is the current that will cause the fuse to break the circuit.
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above / below
Generally you should use a fuse with a rating a few amps the recommended current for the appliance.
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Which of these fuse ratings would be appropriate for a kettle that is designed to operate at 5 A of current?
3 A
5 A
8 A
15 A
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Circuit breakers are like a ________ that can be reset after they break the circuit.
fuse
lamp
cell
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How earth wires protect us from electric shocks:
live / neutral / earth / battery / casing
- The wire is connected to the casing of the appliance.
- If the live wire touches the appliance , the earth wire provides an alternative pathway for electricity to flow.
- This way, we don't get an electric shock from touching the live appliance casing.
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An appliance has 'double insulation'. Therefore it most likely:
Has a plastic casing, but no earth wire
Has both plastic casing and an earth wire
Has neither plastic casing nor an earth wire
Has an earth wire, but no plastic casing
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