Question

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

• A. an iron rod is inserted in the coil.
• B. frequency of the AC source is decreased
• C. number of turns in the coil is reduced.
• D. A capacitance of reactance XC = XL is included in the same circuit.

Answer 1

Answer: (A)

an iron rod is inserted in the coil.

Answer 2

Brightness of the bulb
??decreases when an iron rod is inserted in the coil as impedance of circuit increases.
??increases when frequency of the AC source is decreased as impedance of circuit decreases.
??Increases when number of turns in the coil is reduced as impedance of circuit decreases.

??increases when a capacitance of reactance $X_C = X_L$ is included in the circuit as impedance of circuit decreases