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Alternating Current

Section: Physics

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Question : 13 of 13

Marks: +1, -0

An AC voltage source of variable angular frequency ω and fixed amplitude

V_0

is connected in series with a capacitance C and an electric bulb of resistance R (inductance zero). When ω is increased

[JEE Adv 2010 P1]

the bulb glows dimmer.
the bulb glows brighter.
total impedance of the circuit is unchanged.
total impedance of the circuit increases.

Solution:

The impedance of an RC network is given by

z =

\sqrt{\frac{1}{(\omega C)^2} + R^2}

Thus, whenever there is an increase in angular frequency, the first term in the equation decreases. The power is inversely proportional to resistance. Hence, the bulb glows brighter.

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