Energy dissipation

No system is perfect. Whenever there is a change in a system, energy is transferred and some of that energy is dissipated.

Dissipation is a term that is often used to describe ways in which energy is wasted. Any energy that is not transferred to useful energy stores is said to be wasted because it is transferred to the surroundings.

Electrical cables warming up are a good example of this. It is not useful to have hot wires behind a television as energy is dissipated to the surrounding air.

In a mechanical system, energy is dissipated when two surfaces rub together. Work is done against friction which causes heating of the two surfaces – so the internal (thermal) energy store of the surfaces increases.

New types of electrical component can be more energy efficient such as LED light bulbs as opposed to filament lamps - using these cause less energy to be wasted.

Examples of dissipation

Energy is usually transferred to the internal energy store of the surroundings.

The ways in which energy is dissipated depends on the system:

  • for a radio or set of speakers the electrical work is transferred into useful sound waves and thermal energy is dissipated causing a rise in the internal energy store (temperature) of the surroundings
  • for a tumble dryer, the electrical work is transferred into useful internal (thermal) energy which helps to dry clothes and energy is dissipated wastefully by sound waves which cause a rise in the internal energy store (temperature) of the surroundings
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