Question

A $L$ of $X_L$ is connected in series with a bulb $B$ to an A.C. source as shown in the figure. Briefly explain how does the brightness of the bulb change, when

(i) Number of turns of the inductor is reduced.

(ii) A capacitor of reactance $X_C=X_L$ is included in the same circuit

(iii) If increase driving frequency $f$ in the circuit, does the current amplitude $I$ increase or stay the same?

Answer 1

(i) Increases:

$X_L=\omega L$

As number of turns decreases, L decreases,

hence current through bulb increases / voltage across bulb increases.

(ii) Decreases:

Iron rod increases the inductance, which increases $X_L$,

hence current through the bulb decreases / voltage across bulb decreases.

(iii) Increases:

Under this condition$(X_c=X_L)$

the current through the bulb will become maximum / increase