CIE AS Physics (9702) exams from 2022

Revision Notes

5.1.4 Power

Defining Power

  • The power of a machine is the rate at which it transfers energy
  • Since work done is equal to the energy transferred, power can also be defined as the rate of doing work or the work done per unit time
  • The SI unit for power is Watts (W) where 1 W = 1 J s-1

Power equation, downloadable AS & A Level Physics revision notes

Power is the rate of change of work


  • You may be familiar with labels on lightbulbs which indicate their power such as 60 W or 100 W. These tell you about an energy transferred by an electrical current rather than by a force doing work


Solving Problems Involving Power

Worked example

Worked example - work done per unit time, downloadable AS & A Level Physics revision notes

Exam Tip

Think of power as “energy per second”. Thinking of it this way will help you to remember the relationship between power and energy: “Watt is the unit of power?”

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