The magnetic potential energy, when a magnetic bar of magnetic moment m is placed perpendicular to the magnetic field B is

Two point charges +2μC and -2μC are placed 10 cm apart. The electric field at the midpoint is:

A wire of resistance R is cut into 8 equal pieces. From these pieces two equivalent resistances are made by adding four of these together in parallel. Then these two sets are added in series. The net effective resistance of the combination is :

A constant voltage of 50 V is maintained between the points A and B of the circuit shown in the figure. The current through the branch CD of the circuit is :- 

A parallel plate capacitor made of circular plates is being charged such that the surface charge density on its plates is increasing at a constant rate with time. The magnetic field arising due to displacement current is :

AB is a part of an electrical circuit (see figure). The potential difference " $\mathrm{V}_{\mathrm{A}}-\mathrm{V}_{\mathrm{B}}$ ", at the instant when current $\mathrm{i}=2 \mathrm{~A}$ and is increasing at a rate of $1 \mathrm{amp} / \mathrm{second}$ is :