Electricity in the Home

Pages 52-56

True or false? Mains supply electricity is an alternating current

True

What is the potential difference and frequency of the UK mains supply?

230V

50 cycles per second (50Hz)

Name and give the colours of the 3 wires in a three-core cable

Neutral Wire - Blue

Live Wire - Brown

Earth Wire - Green and Yellow

Give the potential differences for the three wires in a three-core cable

Neutral Wire - 0V

Live Wire - 230V

Earth Wire - 0V

Explain why touching a live wire in dangerous

• Your body is at 0V normally

• If you touch the live wire, a large potential difference is produced and current flows through you

• Large electric shocks like this can injure or kill you

State 3 equations that can be used to calculate electrical power.

1. Energy Transferred (I) = Power (W) x Time (s) [E=Pt]

2. Power (W) = Potential Difference (V) x Current (A) [P=VI]

3. Power (W) = Current² (A) x Resistance (Ω) [P=I²R]

What is the power rating of an appliance?

The maximum safe power that they can operate at

Explain why electricity is transferred by the national grid at a high pd but low current

To reduce the amount of energy lost (as wires heat up)

What are the functions of step-up and step-down transformers?

To increase and decrease the potential difference