Question

An electric bulb having small resistance and a capacitor are joined in series with an AC source whose frequency can be varied. On increasing the frequency of AC source, the glow of the bulb

• A. increases.
• B. decreases.
• C. remains unchanged.
• D. The bulb will not glow at all.

Answer 1

The correct option is A increases.

We know that, when a capacitor of capacitance $\left(C\right)$ is connected across an AC supply of voltage $E=E_0\sin \left(\omega t\right)$, then current in the circuit is $i=E_0\omega C\sin (\omega t+\pi /2)$.

$\Rightarrow i\propto \omega$

Therefore, current increases when the frequency of the AC source is increased, which in turn increases the glow of the bulb.

Hence, option $\left(A\right)$ is the correct answer.