In the given circuit, if the potential at point $B$ is 24 V , the potential at point $A$ is

Two long straight parallel conductors $A$ and $B$ carrying currents 4.5 A and 8 A respectively, are separated by 25 cm in air. The resultant magnetic field at a point which is at a distance of 15 cm from conductor $A$ and 20 cm from conductor $B$ is

Two concentric thin circular rings of radii 50 cm and 40 cm , each carry a current of 3.5 A in opposite directions. If the two rings are coplanar, the net magnetic field due to the rings at their centre is

At a place where the magnitude of the earth's magnetic field is $4 \times 10^{-5} \mathrm{~T}$, a short bar magnet is placed with its axis perpendicular to the earth's magnetic field direction. If the resultant magnetic field at a point at a distance of 40 cm from the centre of the magnet on the normal bisector of the magnet is inclined at $45^{\circ}$ with the earth's field, then the magnele moment of the magnet is