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JEE Advanced · Physics · 22. AC Circuits

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

  1. A the bulb glows dimmer
  2. B the bulb glows brighter
  3. C total impedance of the circuit is unchanged
  4. D total impedance of the circuit increases
Verified Solution

Answer & Solution

Correct Answer

(B) the bulb glows brighter

Step-by-step Solution

Detailed explanation

\(Z=\sqrt{R^2+X_C^2}: I_{\mathrm{rms}}=\frac{V_{\mathrm{rms}}}{Z}: P=I_{\mathrm{rms}}^2 R\) where, \(\quad X_C=\frac{1}{\omega C}\)
As \(\omega\) is increased, \(X_C\) will decrease or \(Z\) will decrease. Hence \(I_{\mathrm{mms}}\) or \(P\) will increase. Therefore, bulb glows brighter.
Hence the correct option is (b).
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