A coil of self inductance $L$ is connected in series with a bulb B and an a.c. source. Brightness of the…
A coil of self inductance $L$ is connected in series with a bulb B and an a.c. source. Brightness of the bulb decreases when
frequency of a.c. source is decreased.
number of turns in the coil is reduced.
a capacitance of reactance $\left(X_L-X_C\right)$ is included in the same circuit.
an iron rod is inserted in the coil.
Solution
When iron rod is inserted, the coil magnetizes the iron rod increasing the magnetic field.
$\therefore \quad$ Inductance (L) of coil increases.
$\mathrm{V}=\mathrm{L} \frac{\mathrm{di}}{\mathrm{dt}}$
$\therefore \quad$ Voltage drop across the coil increases i.e. voltage drop at bulb decreases.
$\therefore \quad$ Brightness of bulb decreases.
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