Question

Using P = Vrms Irms cosδ discuss the special cases for power consumed in an A.C circuit.

Answer 1

Explanation:

Power consumed in an electrical circuit can be given by

$P\ =\ Vrms\times Irms\times cos\delta\del$

where $\delta$ is the angle between voltage and current.

The special cases of power consumed in an AC circuit depends on the value of phase angle between voltage and current.

Case 1: When the circuit is totally resistive

When the circuit is purely resistive the phase angle between voltage and current will zero.

$i.e\ \delta\ =\ 0$

$and\ cos\delta\ =\ 1$

So, the power consumed will be

$P\ =\ Vrms\times Irms\times cos\delta$

$=\ Vrms\times Irms$

Case 2: When circuit is purely reactive

When only inductor or capacitor is connected in the circuit the circuit is called to be purely reactive and in this case the angle between voltage and current will be 90°.

And hence the power consumed by the circuit will be,

$P\ =\ Vrms\times Irms\times cos\delta$

    = 0

So, the power consumption in a purely resistive circuit will be maximum while power consumption in purely reactive circuit will be zero.