Fuses and Earthing Flashcards

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1
Q

What does earthing and fuses prevent?

A

Electrical overloads.

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2
Q

Why is the earth wire and Fuse included in an electrical appliance>

A

For safety reasons.

Protect circuit and wiring.

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3
Q

What happens if somehow a fault occurs?

A

The live wire may touch the metal case then because the case is earthed, too great a current flows in through the live wire, through case and out down the earth wire.

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4
Q

What does the surge in the current do?

A

Melt the fuse when the amount of current is greater than the fuse rating.
CUTS of live supply and breaks the circuit.

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5
Q

What happens when the live supply has been cut of and the circuit breaks?

A

It isolates the whole appliance making it impossible to get an electric shock from the case.
Prevents risks of fires.

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6
Q

What should fuses be rated as?

A

Near as possible but just higher that the normal operating current.

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7
Q

The larger the current…

A

The thicker the cable you need to carry it.

Fuse rating needed for cables usually increases with cable thickness.

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8
Q

What does earthing mean?

A

The case must be attracted to an earth wire.

Earthed conductor never become live.

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9
Q

What is said to be double insulated?

A

If the appliance has a plastic casing and no metal showing.

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10
Q

Anything with double insulation doesnt need what?

A

An earth wire only a live and neutral one.

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11
Q

What are 2-core cables?

A

Cables that only carry the live and neutral wire.

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12
Q

What are circuit breakers?

A

Electrical safety devices used in some circuits.

Protect the circuit from damage if too much current flows.

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13
Q

What happens when circuit breakers detect a surge in a current in a circuit?

A

They break the circuit by opening a switch.

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14
Q

Advantage of circuit breaker?

A

Can easily be reset by flicking a switch on the device.

More convenient then fuses.

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15
Q

Disadvantages of fuses?

A

Have to be replaced once they’ve melted.

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16
Q

Disadvantge of circuit breakers?

A

More expensive then fuses.

17
Q

Name a type of circuit breaker?

A

Residential current circuit breaker.

18
Q

What does the RCCB detect?

A

The difference in current and quickly cuts off the power by opening the switch.

19
Q

RCCB works much faster then fuses.

A

Break the circuit as soon as there is a current surge.

No time wasted for waiting for the current to melt a fuse.

20
Q

How are RCCBs more effective at protecting against electrocution?

A

Work for small current changes that might not be large enough to melt a fuse.
Small current changes would be fatal.