Efficiency

Efficiency is a measure of the useful energy, work, or power that is output from a system, compared to the total energy, work, or power input.
Energy is conserved according to the law of conservation of energy, however, not all energy transferred is usefully employed - some becomes ‘wasted’ as it often transforms into less useful forms such as heat.
Efficiency, therefore, can be increased by reducing energy wastage.

Efficiency is expressed as a fraction between 0 and 1, or as a percentage. An efficiency of 1 or 100% indicates that all input energy is used usefully, whereas an efficiency of 0 signifies all energy is wasted.
To calculate efficiency, you divide useful output energy (or power) by total input energy (or power). This gives a ratio, which for the purposes of GCSE Physics is often multiplied by 100 to express as a percentage.
It is denoted by η and the formula for efficiency is expressed as η= (Useful energy output / Total energy input) x 100%

Reducing friction can increase efficiency by decreasing the energy wasted as heat and sound.
Using insulation can enhance efficiency by limiting thermal energy wastage.
Lubrication can also improve efficiency by reducing friction between moving parts.
The design of objects and devices can often be altered to increase efficiency, such as designing cars with streamlined shapes to lower air resistance.

Maximising efficiency is important in energy conservation, as it can reduce the amount of energy we need to source from the environment.
The greater the efficiency of our appliances and technologies, the less energy we waste, reducing our environmental footprint.
Energy-efficient devices, such as low-energy light bulbs, are crucial in using limited energy resources more sustainably.

Energy transformations are often associated with energy dissipation, where some energy becomes spread out and less available for further use.
For instance, a car engine that’s only 25% efficient converts a quarter of its fuel energy into useful kinetic energy, while the rest becomes wasted energy (such as heat and sound).
In reality, 100% efficiency is virtually impossible to achieve, but improving efficiency is a key goal in many engineering and design tasks.