IIT-JEE 2010 · Paper 1 · Physics Q61

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PhysicsSingle correct+3 / -1Question 61 of 84

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

the bulb glows dimmer

the bulb glows brighter

total impedance of the circuit is unchanged

total impedance of the circuit increases

Answer and worked solution

Official answer: B

Impedance. $Z=\sqrt{R^2+\dfrac1{\omega^2C^2}}$ , which decreases as $\omega$ increases.

Current and power. $I=V_0/Z$ increases, so the power $I^2R$ in the bulb increases: it glows brighter. (C) and (D) are false.

(B)

Topics:Reactance and impedance

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IIT-JEE 2010 · Paper 1, Physics question 61