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Engineering ToolBox > Power

Power is a measure of the rate at which work is done or energy converted

Work done

Power is a measure of the rate at which work is done and can be expressed as

P = W / dt (1)

where

P = power (W)

W = work done (J)

dt = time taken (s)

Since work is the product of the applied force and the distance, (1) can be modified to

P = F v (1b)

where

F = force (N)

v = velocity (m/s)

Energy converted

Power is also a measure of the rate at which energy is converted from one form to another and can be expressed as

P = E / dt (2)

where

P = power (W)

E = energy converted (J)

dt = time taken (s)

Example - Work done by Electric Motor

The work done by a 1 kW electric motor in 1 hour can be calculated by modifying (1) to

W = P dt

    = 1 (kW) 1000 (W/kW) 1 (h) 3600 (s/h)

    = 3600000 J

    = 3600 kJ