Mains electricity

Question 1

describe the graphs for A.C and D.C on a voltage time graph:

Answer 1

A.C = transverse waves (positive and negative frequency)
D.C = straight line

Question 2

how much energy is transferred from the mains?

Answer 2

230v or 50 Hz

Question 3

what colours are the earth neutral and live wires?

Answer 3

earth = green and yellow
neutral = neutral
live = brown

Question 4

why are copper wires used and why are they covered in plastic?

Answer 4

good conductors, plastic is an insulator and is flexible

Question 5

what is the purpose of the cable grip?

Answer 5

holds wires tightly in place so they don’t become loose

Question 6

what is the purpose of the live wire?

Answer 6

connects to the voltage pushing the current in the circuit

Question 7

what is the purpose off the neutral wire?

Answer 7

connected to a voltage close to 0 to ensure that the live wire has a potential difference to push for current

Question 8

purpose of the earth wire?

Answer 8

allows current to flow from the case of a device to the ground (safety feature)

Question 9

what is the purpose of a fuse?

Answer 9

thin metal wire which melts if current is too high

Question 10

what would happen without the earth wire?

Answer 10

live wire becomes loose and a person could get electrocuted if they touch the appliance

Question 11

how does the earth wire provide a low resistance path to the ground? why is this useful?

Answer 11

-made of copper (good conductor)
-current would choose the path of least resistance instead of passing through a person

Question 12

what does a melted fuse do?

Answer 12

breaks the circuit

Question 13

equation for energy:

Answer 13

energy = potential difference × current x timem

E = ITV