Question

In the alternating current shown in the following figure, the currents through inductor and capacitor are $1.2amp$ and $1.0amp$ respectively. The current drawn from the generator is

• A. $0.4amp$
• B. $0.2amp$
• C. $1.0amp$
• D. $1.2amp$

Answer 1

The correct option is B $0.2amp$

If an a.c source $V=V_0\sin \omega t$ is applied across an inductance and capacitance in parallel, current in inductance will lag the applied voltage while across the capacitor will lead
$I_L=\frac{V}{X_L}\sin (\omega t-\frac{\pi }{2})=-1.2\cos \omega t$
$I_C=\frac{V}{X_C}\sin (\omega t+\frac{\pi }{2})=1.0\cos \omega t$
so, the current drawn from the a.c. generator is $I=I_L+I_C$
$=-1.2\cos \omega t+1.0\cos \omega t=-0.2\cos \omega t$
$|I|=0.2A$.