What is Power dissipation?

As power is defined as the rate of energy transfer, 'power dissipation' is a measure of the rate at which energy is dissipated, or lost, from an electrical system. When an electric current does work on a conductor, the internal energy of that conductor increases, causing its temperature to rise above the ambient (surrounding) temperature. This causes energy to dissipate away from the conductor into the surroundings, through the process of heat transfer. The rate of this heat transfer (joules per second) is termed 'power dissipation' (in watts).

This is power that is converted to heat and then conducted or radiated away from the device. Electronic and electric devices can have a limit on the current they can safely handle that is not an electronic limit, but a physical one. For instance, a transistor may otherwise be able to handle a certain amount of current, but it is given a lower current rating because the die gets too hot.

Dissipation is usually measured in watts, and uses the usual Ohm's law calculations for power:

P = I^2 * R

or

P = E * I

Electrical wiring in your house dissipates power, so does the speaker in your stereo, as well as motors, integrated circuits, anything that carries electrical current and has some inherent resistance (which is everything pretty much, except maybe superconductors!).

Power dissipation is usually an unwanted effect, unless you are trying to build an electric heater!

It is wasted power to keep the device quiescent and operational.