Electromagnetic Induction and Alternating Current 6 Question 6
6. An AC voltage source of variable angular frequency $\omega$ and fixed amplitude $V _0$ is connected in series with a capacitance $C$ and an electric bulb of resistance $R$ (inductance zero). When $\omega$ is increased,
(2010)
(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
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Answer:
Correct Answer: 6. (b)
Solution:
- Impedance, $Z=\sqrt{R^{2}+X _c^{2}}, I _{rms}=\frac{V _{rms}}{Z}, P=I^{2 _{rms}} R$ where, $X _C=\frac{1}{\omega C}$ As $\omega$ is increased, $X _C$ will be decrease or $Z$ will be decrease. Hence, $I _{rms}$ or $P$ will increase. Therefore, bulb glows brighter.
