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Power

Power is the rate of energy transfer.

WHenever we have a rate of something, it means ‘how much happens in a certain time’?

For a ‘unit rate’ of something, it means ‘how much happens in one second’.

It therefore also means that the units area going to be ‘something per second’ (e.g. joules per second, ).

We can calculate power using the formula:

Or, in symbols:

Where:

  • is the power, in watts,
  • is the energy transferred, in joules,
  • is the time taken, in seconds,

To calculate energy transferred:

To calculate time taken:

A heater is rated at a power of 2000 W. How much energy does it transfer in 30 minutes?

Section titled “A heater is rated at a power of 2000 W. How much energy does it transfer in 30 minutes?”

A machine transfers 5000 J of energy in 10 s. What is the power of the machine?

Section titled “A machine transfers 5000 J of energy in 10 s. What is the power of the machine?”

A machine has a power of 100 W and transfers 2000 J of energy. How long does it take to transfer the energy?

Section titled “A machine has a power of 100 W and transfers 2000 J of energy. How long does it take to transfer the energy?”