topic 2 - electricity: domestic uses and safety

Question 1

What type of electricity supply is mains electricity?

Answer 1

Alternating current (ac).

Question 2

In the UK, what is the frequency of the domestic electricity supply?

Answer 2

50 Herts (Hz)

Question 3

In the UK, what is the voltage of the domestic electricity supply?

Answer 3

230 Volts (V)

Question 4

What type of electricity supply is mains electricity?

Answer 4

Alternating current (ac).

Question 5

What are the 2 types of electricity supply?

Answer 5

Alternating current (ac) and direct current (dc).

Question 6

Which type of electricity supply is mains electricity?

Answer 6

An ac supply.

Question 7

What type of electricity supply are cells and batteries?

Answer 7

A dc supply.

Question 8

What are alternating currents produced by?

Answer 8

Alternating voltages.

Question 9

What is the difference between alternating and direct potential differences?

Answer 9

In alternating potential differences, the positive and negative ends keep alternating whereas in direct potential differences, they don’t alternate.

Question 10

In the UK, what is the frequency of the domestic electricity supply?

Answer 10

50 Hz

Question 11

In the UK, what is the voltage of the mains electricity supply?

Answer 11

230V

Question 12

How many core cables are appliances connected to the eletricity supply with?

Answer 12

Three.

Question 13

What does the colour of the insulation of each cable show?

Answer 13

Its purpose.

Question 14

What colour is the live wire?

Answer 14

Brown.

Question 15

What colour is the neutral wire?

Answer 15

Blue.

Question 16

What colour is the earth wire?

Answer 16

Green and yellow stripes.

Question 17

What does the live wire provide?

Answer 17

The alternating potential difference from the mains supply.

Question 18

What is the purpose of the neutral wire?

Answer 18

To complete the circuit.

Question 19

What is the purpose of the earth wire?

Answer 19

It is a safety wire which stops the appliance from becoming live.

Question 20

When would the earth wire carry current/

Answer 20

If there was a fault - it doesn’t usually carry current.

Question 21

What is the voltage of the live wire?

Answer 21

230V

Question 22

What is the voltage of the earth wire?

Answer 22

0V

Question 23

What is the voltage of the neutral wire?

Answer 23

0V

Question 24

Why might the live wire be dangerous even when a switch in the main circuit is open?

Answer 24

It can give you an electric shock because even though there is no current flowing, there is still a potential difference in the live wire. If you make contact with the wire, your body would rpovide a link between the supply and the earth and so the current would flow through you.

Question 25

What is the danger in providing any connection between the live wire and earth?

Answer 25

If the link creates a low resistance path to earth, a huge current will flow, which could result in a fire.