Question

An electric lamp, having coil of negligible inductance connected in series with a capacitor and $ac$ source, is glowing with certain brightness. How does the brightness of lamp change on reducing the capacitance?

Answer 1

Impedance of the circuit $Z=\sqrt{R^2+\frac{1}{w^2{C}^2}}$

On decreasing the capacitance, $Z$ increases.

This will decrease the current in the circuit and so, the brightness of the lamp decreases.