Question

A coil of self-inductance L is connected in series with a bulb B and an AC source. Brightness of the bulb decreases when

• A. Number of turns in the coil is reduced
• B. A capacitance of reactance $X_c=X_4$ is induced in the same circuit
• C. An iron rod is inserted in the coil
• D. Frequency is rotate in a magnetic field. The frequency of charge of direction of the induced

Answer 1

The correct option is C An iron rod is inserted in the coil

$\text{Explanation:-}$

The situation is as shown in the figure.

As the iron rod is inserted, the magnetic field inside the coil magnetizes the iron increasing the magnetic field inside it. Hence. the inductance of the coil increases. Consequently, the inductive reactance of the coil increases. As a result, a larger fraction of the applied AC voltage appears across the lnductor, leaving less voltage across the bulb. Therefore' the brightness of the light bulb decreases.

$\text{Hence the correct option is C}$