Mains Electricity

what is an alternating current?

direction of current is constantly changing direction

what is direct current?

current is always flowing in the same direction

what is the chnage in frequency in the UK?

50Hz

what is the average voltage in the UK?

230V

what supplies a direct current?

batteries

name some devices that use AC?

kettle/lamp

name some devices that use DC?

battery operated torch

what is the Earth wire for?

Green and Yellow wire and its a safety wire that takes electricity to earth to prevent you getting a shock

what is the live wire for?

Brown wire which is connected to the fuse, this caries the mains voltage and is the most dangerous

what is the neutral wire for?

blue wire and is on left side of plug this completed the circuit

what is the fuse for?

live wire is connected to the fuse, if current is too high fuse will blow and electricity stops flowing

what is the cable grip for?

makes sure cables dont get broken and keeps wires in place

how does a fuse work?

fuse contains a wire that only lets a certain amount of current through, if fuse melts the current is broken and no electricity flows

equation for power?

power (W) = potential difference (V) x Current (A)

explain how earth wire and fuse work to prevent damage to appliance?

• if a life wire touches the metal casing, current will flow through live, the case and to Earth

• earth has a low resistance so a high current flows

• current has a heating effect and causes temperature of fuse to increase and melt

• this breaks the circuit and stops the current flowing preventing damage to appliance and shock

• if there was no earth wire the current would not increase and fuse would not melt

what is double insulation?

many products don’t have a metal casing but instead are made from insulator like plastic, so electricity can not be conducted from product to person so no Earth wire required