Energy dissipation
No systemAn object or group of objects. is perfect. Whenever there is a change in a system, energyThe capacity for doing work. is transferWhen something is moved from one place to another. This may be people, objects or energy. and some of that energy is dissipatedThe spreading out and transfer of energy stores into less useful forms, such as thermal energy causing the surroundings to heat up. Dissipated energy is often referred to as 'wasted' energy, since it is not transferred to a useful output. .
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 lost 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 frictionA force that opposes or prevents movement and converts kinetic energy into heat. which causes heating of the two surfaces - so the internal (thermal) energy of the surfaces increases. Adding lubricantA lubricant is anything which reduces the friction between two surfaces. between the surfaces reduces this friction and so less heat is wasted, like on a conveyor belt for example.
In an electrical context, new types of components can be more energy-efficient. For example, using LED light bulbs as opposed to filament lamps causes less energy to be wasted.
Examples of dissipation
Energy is usually lost by heating up the surroundings though sometimes energy is dissipated as sound waves.
The ways in which energy is dissipated depends on the system:
- for a radio or set of speakers, the electrical workEnergy transferred by an electric current. is transferred into useful sound waves and infrared radiation is dissipated - ie wasted as heat energy
- for a tumble dryer, the electrical work is transferred into useful internal (thermal) energy which helps to dry clothes - energy is dissipated by sound waves