Domestic uses and safety

Question 1

What do cells and batteries supply to a circuit

Answer 1

Current that flows in one direction (direct current)

Question 2

what is alternating current

Answer 2

Current that repeatedly reverses its direction

Question 3

What is frequency in regards to AC

Answer 3

The rate at which the current reverses its direction

Question 4

What is the frequency of the UK’s mains supply and what does it mean

Answer 4

1) 50Hz

2) The current reverses direction 50 times each second

Question 5

What is the equation for calculating frequency

Answer 5

1
Frequency = —————————
Time taken for 1
cycle

Question 6

How does the live wire of the mains supply alternate

Answer 6

Between a positive and negative PD

Peaks at +325V and -325V

Question 7

What is the potential of the neutral wire

Answer 7

0V

Question 8

What is the national grid

Answer 8

System of cables and transformers linking power stations to homes

Question 9

Why are the pins of a plug made from brass (3 reasons)

Answer 9

1) Good electrical conductor
2) hard
3) won’t rust/oxidise

Question 10

What is the colour of these wires in a plug:
A) neutral
B) earth
C) live

Answer 10

A) blue
B) green and yellow
C) brown

Question 11

What is the purpose of the fuse in a plug

Answer 11

Melts if current grows too high, cutting of current to live wire

Question 12

How are metal appliances ‘earthed’

Answer 12

1) Case attached to earth wire in cable

2) Stops metal case from becoming live if live wire breaks and touches it

Question 13

When does a plug not require an earth wire and what is this type of plug called

Answer 13

1) When the appliance has a plastic case (is double insulated)
2) A two-core cable

Question 14

When does a cable need to be thicker

Answer 14

When the current is larger

Question 15

Which pin is longest and why

Answer 15

Earth pin —> connects to socket first