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

Options

A. An iron rod is inserted in the coi
B. Frequency of the AC source is decreased
C. Number of turns in the coil is reduced
D. A capacitance of reactance `X_(C) = X_(L)` is included in the same circuit

Answer

A

Explanation

As iron rod is inserted in the coil
Self inductance (L) is increased as
`L = mu_(0) mu, n^(2) Al rArr L prop mu_(r)`
Since `L uarr X_(L) uarr , I darr`
Hence, brightness of the bulb decreases.