Mains electricity

Question 1

direct current

Answer 1

an electric current that always flows in one direction e.g. electronic circuits in computers and stereos

Question 2

alternating current

Answer 2

an electric current that is constantly changing direction, it’s produced by most generators and is used in mains electricity e.g. motors

Question 3

what are the different parts of a plug and their colours?

Answer 3

-earth wire (green/yellow)
-live wire (brown)
-neutral wire (blue)
-fuse
-cable grip
-outer insulation

Question 4

what’s the function of a live wire?

Answer 4

carries p.d. from the supply and is connected to the fuse

Question 5

what’s the function of the neutral wire?

Answer 5

completes the circuit

Question 6

what’s the function of the earth wire?

Answer 6

the safety wire (stops the appliance becoming live)

Question 7

how do fuses work?

Answer 7

-a fuse contains a thin wire, which melts if the current is too high
-this breaks the circuit and so electricity is unable to flow through the appliance
-the appliance stops working and any danger has been averted
-fuses act as an early warning system, preventing appliances from being damaged by surges in electricity and warning owners of faults

Question 8

what is the average voltage of the mains supply in the UK?

Answer 8

230 volts

Question 9

what is the mains frequency?

Answer 9

50 Hertz

Question 10

describe the oscilloscope trace for direct current

Answer 10

a raised line that flows in one direction

Question 11

describe the oscilloscope trace for an alternating current

Answer 11

a wavy line that changes direction back and forth