Energy and Power


The amount of energy transferred in a circuit can be calculated by:

E = I x V x t

  • E - Energy, J
  • I - Current, A
  • V - Potential Difference, V
  • t - Time, s


Power is the rate of energy transfer per second.

You need to be able to recall the following equation:

P = E / t

  • P - Power; Watts, W
  • E - Energy, J
  • t - Time, s

Power 2

We can also calculate power via these equations too:

P = I x V


P = I2 x R

Calculate the power of a light bulb that converts 600J in 2 minutes
What is the resistance of a motor that has a power rating of 400W with a current of 2A?
100 Ohms
A 5V battery is used for 3 minutes. A students ammeter reads 4A whilst the batter is used. How much energy is given to the circuit?