Question

An electric bulb and a capacitor are connected in series with an $AC$ source. On increasing the frequency of the source, the brightening of the bulb will,

• A. increase
• B. decrease
• C. remain unchanged
• D. sometimes increase and sometimes decrease

Answer 1

The correct option is A increase



$P=I^{2}R={\left(\frac{E_{rms}}{Z}\right)}^{2}R$
Here, $Z=\sqrt{R^2+X_C^2}=\sqrt{R^2+{\left(\frac{1}{\omega C}\right)}^2}$

As $\omega$ is increased, $Z$ decreases, so that, $P$ increases. So, the brightness of the bulb will also increase.

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