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An a.c. voltage source of variable angular frequency w and fixed amplitude V, is connected in series with a capacitance C and an electric bulb of resistance R (inductance zero). When a is increased.

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

Solution :Here impedance`Z = sqrt(R^(2) + X_(C)^(2)) = sqrt(R^(2) + 1/(C^(2)OMEGA^(2))`· As frequency o increases, capacitive reactance XC and consequently impedance of circuit decreases and so the circuit CURRENT increases. As a result the bulb glows brighter.


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