Electricity in the home

What is the difference between AC and DC current?

AC- flows in both directions

DC- flows in one direction (not the reverse)

What are the 3 different wires in a plug?

1. Live wire- brown
2. Neutral wire- blue
3. Earth wire- green and yellow stripes

What are the purposes of each wire?

1. Live wire- carries the alternating potential difference from the supply
2. Neutral wire- completes the circuit
3. Earth wire-safety measure that stops the appliance from becoming live

What is the potential difference of each wire?

Potential difference of live wire and earth wire is 230V

Neutral wire is close to or at earth wire at 0V

The earth wire is 0V as it only carries charge when there is a fault

How can a live wire be dangerous even if the circuit is open?

Even if the circuit is open it can accidentally become closed, by a human touching it maybe as they are standing on the floor which is connected to the earth

What are the dangers of having any connection between the live wire and the earth wire?

A shock or fire would be highly likely

What are the two equations for power?

1. power= potential difference x current \[P=IV\]
2. power= (current)^2 x resistance \[P=I^2R\]

Name an example of an energy transfer of a domestic appliance

A light bulb’s energy transfer is:


1. electrical energy store (battery)→ thermal energy store (dissipated to surroundings) → light energy

What are the equations for energy transferred

1. energy transferred = power x time \[E=QV\]
2. energy transferred = current x potential difference \[E=QV\]

What is the national gird?

it is a system of cables and transformers linking power stations to consumers

What are step-up transformers?

they are used to raise the potential difference of the power stations to the transmission cable

What are step-down transformers?

they are used to lower the potential difference of the transformer cable to the consumer to a much lower level

Why is the national grid system efficient?

1. high voltage means low current for the same amount of power (P=IV)
2. higher current causes heating which means energy lost which is less efficient so low current is more efficient