The magnetic energy stored in an inductor of inductance $4\,\text{H}$ carrying a current of $1.5$ A is

When a.c. source is connected across a pure capacitor, the correct phase relation between current and emf is shown in figure.

In series LCR circuit $R = 10\,\Omega$ and impedance is $30\,\Omega$. An r.m.s. voltage $210$ V, is applied across the circuit. The true power consumed in AC circuit is

Light travels a distance 'x' in time '$t_0$' in air and '$4x$' in time '$t_1$' in another denser medium. The critical angle for this medium is