Question

Same current is flowing in two alternating circuits. The first circuit contains only inductance and the other contains only a capacitor. If the frequency of the e.m.f. of ac is increased, the effect on the value of the current will be

• A. Increases in the first circuit and decreases in the other
• B. Increases in both the circuits
• C. Decreases in both the circuits
• D. Decreases in the first circuit and increases in the other

Answer 1

The correct option is D Decreases in the first circuit and increases in the other

For the first circuit $i=\frac{V}{Z}=\frac{V}{\sqrt{R^2+{\omega }^2{L}^2}}$
$\therefore$ Increase in $\omega$ will cause a decrease in i.
For the second circuit $i=\frac{V}{\sqrt{R^2+\frac{1}{{\omega }^2{C}^2}}}$
$\therefore$ Increase in w will cause an increase in i.