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