2.4 Using Mains Electricity Safely and the Power of Electrical Appliances

Question 1

What is a.c and what does it do?

Answer 1

Alternating current - current moves in both directions

Question 2

What does d.c stand for and what is it?

Answer 2

Direct current - Current moves in one direction

Question 3

What is the current and voltage of the UK mains supply?

Answer 3

50Hz and 230V

Question 4

What uses a.c?

Answer 4

Mains supply

Question 5

What uses d.c?

Answer 5

Cells and batteries

Question 6

What does the brown wire do in a plug?

Answer 6

Live wire - carrys the main supply, alternates between 230V and -230V

Question 7

What does the blue wire do in a plug?

Answer 7

Neutral wire - always at 0V

Question 8

What does the green/yellow wire do in a plug?

Answer 8

Earth wire - for safety, carries electricity to earth

Question 9

What are the pins made of and why?

Answer 9

Brass because it’s strong and it conducts electricity

Question 10

What does the fuse do in a plug?

Answer 10

It will melt if the current is too high, this stops the live supply and breaks the circuit

Question 11

What do fuses and earth wires prevent?

Answer 11

Electric shocks, fires and the appliances wiring

Question 12

What can be used instead of a fuse?

Answer 12

Residual Current Circuit Breaker (RCCS)

Question 13

What does a RCCS do?

Answer 13

If the current is too great it opens a switch to break the circuit

Question 14

What are the advantages and disadvantages of RCCS’ over fuses?

Answer 14

Advantages:

• Can easily be reset instead of having to get a new fuse
• Break the circuit quicker
• Can detect smaller increases in current

Disadvantages:

• Expensive

Question 15

What does double-insulation mean?

Answer 15

There’re no metal parts of a case showing

Question 16

What do resistors produce when current flows through them?

Answer 16

Heat

Question 17

What’s the unit for charge?

Answer 17

C (Coulombs)