(2) Domestic Uses and Safety

Question 1

Define AC

Answer 1

AC stands for alternating current - the current changes direction (50 times a second)

• the mains supply is the uk is AC

Question 2

Define DC

Answer 2

DC stands for direct current- the current only flows in one direction

• Batteries and cells supply DC

Question 3

What is the frequency and voltage of the uk mains electricity?

Answer 3

Frequency = 50Hz
Voltage = 230V

Question 4

What are the wires in a plug?

Answer 4

1. Live wire
2. Neutral wire
3. Earth wire

Question 5

State the insolation colour used on the 3 wires in a plug

Answer 5

Live wire = Brown
Neutral wire = Blue
Earth wire = green and yellow stripes

Question 6

How do fuses work?

Answer 6

Fuses have a rating based on the amount of current they will allow through, if more than this tries to flow through the wire heats up and melts, breaking the circuit and protecting the appliance

Question 7

What is a circuit breaker?

Answer 7

Circuit breakers measure the difference in current in the live and neutral wires, if the difference is too great they stop the flow of current

Question 8

When does the Earth wire carry a current?

Answer 8

• normally there is no current flowing through

• of a fault occurs in the appliance, current will flow to the ground

Question 9

Sate the potential difference between the live and earth wires

Answer 9

230 volts

Question 10

What is the purpose of the neural wire?

Answer 10

To complete the circuit by connecting the appliance to the mains supply

Question 11

What is the potential difference of the neutral wire?

Answer 11

0 volts

Question 12

How do you work out frequency?

Answer 12

Frequency = 1 ÷ how long 1 wave takes

Question 13

For metal appliances, where is the earth wire connected to?

Answer 13

It’s connected to the metal casing of the appliance so that if the live wire becomes loose and touches the casing the current will flow thought the earth wire, preventing electrocution