Power Efficiency Calculations - GCSE Physics | kayscience.com

A device is useful because the device can transfer energy from one useful energy store to another useful energy store.

However no device is 100% efficient. This is because the device will transfer energy to non-useful energy stores.

The energy that isn’t transferred to a useful energy store is called wasted energy, or dissipated energy. The useless energy stores are usually thermal energy stores of the surroundings.

The higher the efficiency of a device the less energy is being transferred to the useless surrounding energy stores

The equation for the efficiency of an energy transfer in terms of power is:

efficiency = useful output power transfer ÷ total input power transfer
. .

Rearrange the equation for the useful output energy transfer in terms of power is:

useful output power transfer = efficiency x total input power transfer


Rearrange the equation for the total input energy transfer in terms of power is:

total input power transfer = efficiency x useful output power transfer

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Thank you so much! This helped a lot in Science ^^. Just a question, if we had to work out the total power input would we use the same method?