In the given circuit, the equivalent resistance between $A$ and $B$ is

A square loop of side $a$ and carrying a current $I$ is suspended from an insulating hanger of a spring balance as shown in figure. The transverse magnetic field $B$ directed into the paper occurs only at the bottom side of the loop. When direction of current in the loop is reversed, the change in the reading of spring balance is

A current carrying loop is placed in a uniform magnetic field $B$ in different orientations I, II, III and IV as shown in the figure. The correct order of decreasing potential energy is

( $\hat{\mathbf{n}}=$ unit vector normal to the plane of the loop)

A bar magnet of magnetic moment $2 \mathrm{~A}-\mathrm{m}^2$ lies aligned with the direction of a uniform magnetic field of 0.3 T . The amount of work required by an external torque to turn the magnet so as to align its magnetic moment normal to the field direction is