CP9 Household Circuits Flashcards
What is power measured in?
watt, w
What is a direct current and what devices supply a direct current?
a movement of charge in only 1 direction. Cells and batteries supply direct current
What is an alternating current?
the movement of charge changes direction
What frequency is UK mains electricity supplied at?
50Hz
What voltage is UK mains electricity supplied at?
230V
Is UK mains electricity d.c or a.c.?
a.c.
In a plug what is the live wire for and what voltage should it be at?
The live wire connects the appliance to the generators at the power station. It should be at 230V.
In a plug what is the neutral wire for and what voltage should it be at?
The neutral wire is the return path to the power station. It should be at 0V.
What is each end of the earth wire connected to and what voltage should it be at?
The earth wire is connected to the metal case of an appliance at one end and a metal stake pushed into the ground at the other.
The earth wire should be at 0V.
What dangerous event could happen if a fault in an appliance causes a very large current to flow?
Large currents get very hot (like in the filament bulb) and can potentially start a fire.
What is the purpose of a fuse or circuit breaker?
If a current above a safe value passes through a fuse or circuit breaker it will blow or trip breaking the circuit
What is the purpose of the earth wire?
To keep the metal case of an appliance at 0V so in the case of a fault it can’t cause an electric shock.
What would happen if the live wire flowed through to the earth wire?
Because there would be very low resistance as there are no components in the circuit a very large current would flow blowing the fuse or circuit breaker.
Whereabouts in a household circuit should fuses/circuit breakers be connected and why?
Fuses and circuit breakers should be connected to the live wire so they protect the entire circuit from that point on if there is a fault.
