What is "watt second"

n. a unit of electrical energy equal to the work done when a current of one ampere passes through a resistance of one ohm for one second [syn: joule, J]

A watt second (also watt-second, symbol W s or W·s) is a derived unit of energy equivalent to the joule. The watt-second is the energy equivalent to the power of one watt sustained for one second. While the watt-second is equivalent to the joule in both units and meaning, there are some contexts in which the term "watt-second" is used instead of "joule".

The kilowatt hour (kWh) is equivalent to 3,600,000 watt-seconds and is a unit used in the electricity market, and by producers of electricity.

Although joule and watt-second mean exactly the same thing (they represent the same amount of the same physical quantity, viz. energy), the newton metre is not equivalent to the joule (despite having the same dimensions) as it represents torque rather than energy. (In terms of vectors, torque is a cross product of force and distance, and energy is their dot product.)