Answer Posted / ayub
By defenition , power factor is the cosine of the phase
angle between voltage and current in any electric circuit
Suppose we have an electric circuit to which an AC supply
is applied . Now the flow of current depends on the circuit
constants like Resistance, inductance ,Capacitance of the
circuit
Now if the circuit is purely resistive in nature, then we
see that the AC current flowing through the circuit has got
the same variation as that of the Voltage at the same time
ie the current reaches the maximum value at the same time
the voltage reaches the maximum value and so on . here we
say that the voltage and current is in phase
Now if the circuit is purely inductive, then the current
reaches the maximum after 1/4 of time of one cycle and so
on . In this case the current is said to be lagging the
voltage . The fundamental reason for this time lag is the
property of the inductor by which it doesnot allow any
sudden change of current through it
Finally, if the circuit is purely capacitive in nature then
in such circuit we will see the voltage lagging the current
(in otherwords current is leading the voltage )by 1/4 th
cycle . The basic reason is that when the capacitor is
getting charged from zero ,the current will be maximum
initially and it reduces to zero when the capacitor is
fully charged .ie the current is maximum when the voltage
across it is zero and so on ( or otherwise capacitor will
not allow any sudden voltage acoss it
The foregoing expalnations are put in mathematical form to
define power factor as described in the first paragraph
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