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Power in an AC circuit is considered one of the most asked concept.
32 Questions around this concept.
For the LCR circuit, shown here, the current is observed to lead the applied voltage. An additional capacitor C', when joined with the capacitor C present in the circuit, makes the power factor of the circuit unity. The capacitor C', must have been connected in :
Power in an AC circuit-
From the previous concept, we can say that the voltage v = vm sinωt applied to a series RLC circuit drives a current in the circuit given by i = im sin(ωt + φ) where,
So, the instantaneous power is equals to -
If we calculate the average power, then the second term of RHS will become zero. Because it is time dependent and during one complete cycle, the summation will become zero.
From the above equation we can see that the average power dissipated depends on the voltage and current and the cosine of the phase angle φ between them. The quantity cosφ is called the power factor.
Let us discuss the power factor for various cases -
So, may be non-zero in R-L, R-C or R-L-C. And if it is non-zero, then there must be some power dissipation but that power dissipation is only in resistor.
Important point -
Apparent or virtual power - The product of apparent voltage and apparent current in an electrical circuit. Apparent power be always positive
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