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power is the amount of energy transferred or converted per unit of time. In the International System of Units, the unit of power is the watt, equal to one joule per second. In older works, power is sometimes called activity. Power is a scalar quantity.
SI unit: Watt
Types
There are four main types of power transmission – mechanical, electric, hydraulic and pneumatic.
The most common mechanical power transmission methods in use in the engineering industry today are:
Shaft couplings.
Chain drives.
Gear drives.