# Energy and Power

## Energy

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

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**

And

**P = I2 x R**

- Calculate the power of a light bulb that converts 600J in 2 minutes
- 10W
- 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?
- 3600J