If current of 4 A produces magnetic flux of $3 \times 10^{-3}$ Wb through a coil of 400 turns, the energy stored in the coil will be

The equivalent inductance between A and B is equal to

A series combination of resistor 'R' and capacitor 'C' is connected to an a.c. source of angular frequency '$\omega$'. Keeping the voltage same, if the frequency is changed to $\left(\dfrac{\omega}{3}\right)$ the current becomes half of the original current. Then the ratio of capacitive reactance and resistance is

In the series LCR circuit shown in figure the impedance is