CIE A Level Physics復習筆記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 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
A car engine exerts the following force for 1.0 km in 200 s.
What is the average power developed by the engine?
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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