Mains electricity - AQA SynergyPower, potential difference and current

Electricity can flow either as direct or alternating current, and is used in homes to power electrical appliances. The National Grid distributes electricity throughout the country.

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Power, potential difference and current

Heating up wires

The amount of energy transferred each second () between the can be calculated using the equation:

power = potential difference × current

\(\text P = \text V \times \text I\)

This is when:

  • power (\(\text{P}\)) is measured in watts (W)
  • (\(\text{I}\)) is measured in amps (A)
  • (\(\text{V}\)) is measured in volts (V)

One watt is equal to one joule per second (J/s).

Power can also be written as:

power = (current)2 × resistance

\(\text{P} = \text{I}^{2} \times \text{R}\)

This is when:

  • power (\(\text{P}\)) is measured in watts (W)
  • current (\(\text{I}\)) is measured in amperes, often referred to as amps (A)
  • (\(\text{R}\)) is measured in ohms (Ω)

Example

How much energy is transferred each second by a current of 2 amps (A) driven by a potential difference of 230 volts (V)?

\(\text P = \text I \times \text V\)

= 2 × 230

\(\text{P}\) = 460 W

Question

What power is dissipated by a current of 3 A through a 10 Ω resistor?

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