Why the unit of active power in watt?

Answer 1

The unit of power is the watt. It means joules per second. It was established that way by convention.

Many of our "common" units are actually combined units, combined for convenience sake. The ampere is coulombs per second. The volt is joules per coulomb. The ohm is joules-seconds per coulomb squared. And so on and so forth...

Answer">Answer

'Active power', 'true power', and 'real power', are alternative names for the rate at which work in done by an AC load, and is measured in watts. To differentiate apparent power and reactive power from active power, these quantities are expressed in volt amperes and reactive volt amperes -where apparent power is the vector sum of active power and reactive power

Further to the original answer, while it is perfectly correct that some units, like the watt, have been given special names -in this case, to replace 'joule per second'- this is notactually the case for the ampere, which is defined in terms of the force between two current-carrying conductors. The ampere is an SI Base Unit and, so, is not a 'special name' for a 'coulomb per second'. In fact, it is the coulomb which is a special name for an ampere second.