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7. Alternating current — Physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 SciencePhysics7. Alternating current1 Mark
MCQ
An $A C$ voltage source of variable angular frequency $\omega$ and fixed amplitude $V_0$ is connected in series with a capacitance $\mathrm{C}$ and an electric bulb of resistance $\mathrm{R}$ (inductance zero). When $\omega$ is increased
  • A
    the bulb glows dimmer
  • ✓
    the bulb glows brighter
  • C
    total impedance of the circuit is unchanged
  • D
    total impedance of the circuit increases
✓

Answer

Correct option: B.
the bulb glows brighter
b
Impedance $Z=\sqrt{\frac{1}{(\omega C)^2}+R^2}$

as $\omega$ increases, $Z$ decreases.

Hence bulb will glow brighter

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