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 $(P)=V_{\text{rms }}{I}_{\text{ rms }}\cos \varphi$
where $\varphi$ 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, $\varphi =90^{\circ }$
$\therefore <P⟩=V_{\text{rms}}{I}_{\text{rms }}\cos 90^{\circ }$
$=0$
$\left(\because \cos 90^{\circ }=0\right)$