Exams › JEE Main › Physics
An AC source of fixed amplitude V0 and variable angular frequency omega is connected in series with a capacitor C and a bulb of resistance R (no inductance). As omega is increased, what happens?
- The bulb glows dimmer
- The bulb glows brighter
- The total impedance of the circuit is unchanged
- The total impedance of the circuit increases
Correct answer: The bulb glows brighter
Solution
The series impedance is Z = sqrt(R² + (1/(omega*C))²). Increasing omega reduces the capacitive reactance 1/(omega*C), so Z decreases, the current increases, and the power dissipated in the bulb (I²*R) rises - the bulb glows brighter.
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