Flashcards in Fuses and Earthing Deck (14):
What will happen if the live wire touches the metal case?
Because the case is earthed, The current flows in through the live wire through the case and out down the earth wire. Creating a surge
What happens when there is a surge of current?
A surge in current melts the fuse when the amount of current is greater than the fuse rating. This cuts off the live supply and breaks the circuit.
What do fuses prevent from happening?
They isolate the whole appliance making it impossible to get an electric shock from the case therefore preventing the risk of fire caused by the heating affect of a large current
If an appliance has a plastic casing and no metal parts showing what is it said to be?
What are circuit breakers?
Circuit breakers are an electrical safety device used in some circuits to protect the circuit from damage if too much current flows
How do circuit breakers work?
When circuit breakers detect a surge in current in a circuit, they break the circuit by opening a switch
What is an advantage of using circuit breakers over fuses?
A circuit breaker can easily be reset by flicking a switch on the device . This makes them more convenient than fuses -which have to be replaced once they've melted
What is a type of circuit breaker used instead of a fuse and earth wire?
Residual current circuit breakers
How does a RCCB work?
In an RCCB , it detects a difference in current and quickly cuts off the power by opening a switch
What is an advantage of RCCB's as opposed to fuses? (2)
RCCB's operate much faster than fuses. They break the circuit as soon as there is a current surge. No time is wasted to melt a fuse which makes them safer.
How are RCCB's more effective than fuses at preventing electrocution?
Small current changes could be fatal. As RCCB's work for even small current changes , but fuses only work for large current changes, RCCB's are more effective at preventing potential electrocution.
Appliance with double insulation don't need which type of wire?
Which type of safety device contains a wire that is designed to melt when the current passing through it goes above a certain value?