Question

The power loss in pure inductor in an $A.C$. circuit will be:

• A. $V_{\text {rms }} I_{\text {rms }}$
• B. more
• C. zero
• D. none of these

Answer 1

Answer: (C)

The average power loss in A.C. circuit $(P)=V_{ \text{rms }} I_{\text{ rms }} \cos \phi$
where $\phi$ is the angle between $V_{\text{rms }}$ and $I_{\text {rms }}$.
In an $A.C$. circuit, the potential difference across pure inductor leads the current in phase by $90^{\circ} .$
So, $\phi=90^{\circ}$
$\therefore < P\rangle =V_{\text{rms}} I_{\text{rms }} \cos 90^{\circ} $
$=0 $
$\left(\because \cos 90^{\circ}=0\right)$