Question

A lamp is connected in series with a capacitor and an AC source. What happens if the capacity of the capacitor is reduced?

• A. The lamp shines more brightly
• B. The lamp shines less brigthly
• C. There is no change in the brightness of the lamp
• D. Brightness may increase or decrease depending on the frequency of the AC

Answer 1

Answer: (B)

The lamp shines less brigthly

The lamp shines less brightly because, when capacity of the capacitor is reduced, the capacitive reactance $X_c=\frac{1}{\omega C}$ increases. Hence, impedance $Z$ increases resulting in decrease in current.

The power for the resistor $i^{2}R$ decreases, hence the lamp shines less brightly.