Power

What is power?

Power is the rate of work done or energy conversion. SI unit of power is the watt (W)

What is Efficiency?

• The efficiency of a machine is how much useful energy is used or stored in a machine when compared to the amount of energy provided.

Classic Efficiency Questions

1. Explain why in practical, the actual useful work done by a motor is less than the calculated value.

• Some mechanical energy is converted to thermal energy as it is used to overcome frictional force.
• Some energy is also converted to sound energy.
• The thermal energy and sound energy is lost to the surroundings.
• Therefore, the actual useful work done is always less than the calculated value.