Efficiency

Efficiency

A measure of how good a device is at transferring energy input to useful energy output

Total input energy

The total amount of energy supplied to a device

Useful energy output

The amount of energy that is transferred to useful energy stores

Wasted energy output

The amount of energy that is wasted or dissipated to the surroundings

Efficient device

A device that wastes very little of its input energy

Inefficient device

A device that wastes most of its input energy

Efficiency \= useful output energy transfer ÷ total input energy transfer

The equation linking efficiency, useful output energy transfer and total input energy transfer

Efficiency \= useful power output ÷ total power input

The equation linking efficiency, useful power output and total power input

Percentage efficiency

Found by multiplying the efficiency by 100

What is meant by an efficiency greater than 1 or 100%

More energy is being transferred than is being supplied

Why can't you have an efficiency greater than 1 or 100%

This would would break the law of conservation of energy as it would mean that energy is being created

Reasons devices waste energy

1) Friction between their moving parts 2) Heat due to electrical resistance 3) Unwanted sound or light

How to improve efficiency

Reduce the amount of energy that a device wastes or dissipates to the surroundings

Ways to improve efficiency

1) Lubricate mechanical devices to reduce the friction between moving parts of the machine 2) Insulate heating devices to reduce the dissipation of thermal energy to the surroundings