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

Answer: (D)

Decreases in the first circuit and increases in the other

Answer 2

For the first circuit $i = \frac{V}{Z} = \frac{V}{\sqrt{R^{2} + \omega^{2}L^{2}}}$

$\therefore$ Increase in ω 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 ω will cause an increase in i.