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 the $\mathrm{AC}$ source is decreased
number of turns in the coil is reduced
a capacitance of reactance $X_C=X_L$ is included in the same circuit
an iron rod is inserted in the coil
Solution
As $Z=\sqrt{R^2+X_L^2}=\sqrt{R^2+(2 \pi f V L)^2}$
As $I=\frac{V}{Z}, P=I^2 R$
i.e., $V \uparrow, L \uparrow \Rightarrow Z \uparrow, I \downarrow$ and $P \downarrow$