Question

An AC voltage source of variable angular frequency to and fixed amplitude $V_0$ is connected in series with a capacitance $C$ and an electric bulb of resistance $R$ (inductance zero). When to is increased

• A. the bulb glows dimmer
• B. the bulb glows brighter
• C. total impedance of the circuit is unchanged
• D. total impedance of the circuit increases

Answer 1

Answer: (B)

the bulb glows brighter

Answer 2

$Z = \sqrt{R^2 + X^2_c} : I_{rms} = \frac{V_{rms}}{Z} : I^2_{rms}R$
where, $X_C = \frac{1}{\omega C}$
As(0 is increased, X c will decrease or Z will decrease. Hence
Ims or P will increase. Therefore, bulb glows brighter.
Hence, the correct option is (b).