Page 840 - Basic Electrical Engineering
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11.10.1 Power in dc and ac Circuits
Power is the product of voltage and current. In dc circuits, P = V × I, where
dc
V is the voltage across the load and I is the current flowing through the load.
In ac circuits, power is the product of instantaneous value current and
instantaneous value voltage. Thus, in an ac circuit with R–L load
AC Power,
p = ν × i
where
ν = V sin ωt
m
and
i = I sin (ωt − ϕ)
m
ϕ = power factor angle
Substituting
Average power is calculated over one cycle.
Thus,
