An electric bulb,an open coil inductor,an $AC$ source,and a key are all connected in series to form a closed circuit. The key is closed and after some time,an iron rod is inserted into the interior of the inductor. Then:

$A$ current of $\frac{25}{\pi} \text{ Hz}$ frequency is passing through an $AC$ circuit having a series combination of $R=100 \ \Omega$ and $L=2 \text{ H}$. The phase difference between voltage and current is . . . . . . . (in $^{\circ}$)

An e.m.f. $E=4 \cos (1000 t)$ volt is applied to an $LR$ circuit of inductance $3 \ mH$ and resistance $4 \ \Omega$. The maximum current in the circuit is

In an $AC$ circuit,the potential differences across an inductance and a resistance joined in series are $16 \, V$ and $20 \, V$ respectively. The total potential difference of the source is .......... $V$.

$A$ $100 \;\mu F$ capacitor in series with a $40 \;\Omega$ resistance is connected to a $110 \;V, 12 \;kHz$ supply.
$(a)$ What is the maximum current in the circuit?
$(b)$ What is the time lag between the current maximum and the voltage maximum?
Hence,explain the statement that a capacitor is a conductor at very high frequencies. Compare this behaviour with that of a capacitor in a $dc$ circuit after the steady state.

$A$ circuit connected to an $ac$ source of $emf$ $e = e_0 \sin(1000t)$,where $t$ is in seconds,exhibits a phase difference of $\frac{\pi}{4}$ between the $emf$ $e$ and current $i$. Which of the following circuits will exhibit this?