Fuses and Earthing Flashcards
What does earthing and fuses prevent?
Electrical overloads.
Why is the earth wire and Fuse included in an electrical appliance>
For safety reasons.
Protect circuit and wiring.
What happens if somehow a fault occurs?
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.
What does the surge in the current do?
Melt the fuse when the amount of current is greater than the fuse rating.
CUTS of live supply and breaks the circuit.
What happens when the live supply has been cut of and the circuit breaks?
It isolates the whole appliance making it impossible to get an electric shock from the case.
Prevents risks of fires.
What should fuses be rated as?
Near as possible but just higher that the normal operating current.
The larger the current…
The thicker the cable you need to carry it.
Fuse rating needed for cables usually increases with cable thickness.
What does earthing mean?
The case must be attracted to an earth wire.
Earthed conductor never become live.
What is said to be double insulated?
If the appliance has a plastic casing and no metal showing.
Anything with double insulation doesnt need what?
An earth wire only a live and neutral one.
What are 2-core cables?
Cables that only carry the live and neutral wire.
What are circuit breakers?
Electrical safety devices used in some circuits.
Protect the circuit from damage if too much current flows.
What happens when circuit breakers detect a surge in a current in a circuit?
They break the circuit by opening a switch.
Advantage of circuit breaker?
Can easily be reset by flicking a switch on the device.
More convenient then fuses.
Disadvantages of fuses?
Have to be replaced once they’ve melted.
