Dissipation
No systemAn object or group of objects. is perfect. Whenever there is a change in a system, energyThe capacity for doing work. is transferred 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 through thermal energy
In a mechanical system, such as a conveyor belt, 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. The thermal energy store of the surfaces increases, so energy is dissipated rather than being usefully transferred. A lubricantA lubricant is anything which reduces the friction between two surfaces. between the surfaces reduces this friction, meaning less energy is wasted.
New electrical products tend to be more energy efficient than older designs. For example, LED light bulbs are more efficient than filamentA thin, high resistance wire that gets hot and glows when a current flows through it causing it to emit heat and light. Filaments are used in some types of bulb and electrical heaters. lamps because a larger proportion of the electrical energy store is transferred to the surroundings by light rather than by heating.
Dissipation through sound energy
In a tumble dryer, electrical work is transferred into useful thermal energy, which helps to dry clothes. However, energy is dissipated by vibrations, which we call sound waves. This is why tumble dryers can be very noisy.
Electrical generators are also very noisy. Some of the electric and magnetic energy store of the generator is dissipated by vibrations as the generator spins. We sense these vibrations as sound.