Question

The average power lost in pure capacitor in an $A.C$. circuit:

• A. is zero
• B. depends on V
• C. depends on C
• D. depends on insulator placed in parallel plate capacitor

Answer 1

Answer: (A)

Average power of A.C. circuit
$P_{av}=V_{\text{rms }}\times I_{\text{rms }}\cos \varphi$
If circuit contains only capacitor, then
$\varphi =-\frac{\pi }{2}$
$\therefore \cos \varphi =\cos \left(-\frac{\pi }{2}\right)=0$
so, $P_{av}=0$