Exercise (Assertion & Reason)

If number of turns, area and current through a coil are given by $n, A$ and $I$ respectively, then its magnetic moment is given by

Magnetic permeability is maximum for

The magnetic susceptibility of the following is

A dip circle is taken to geomagnetic equator. The needle is allowed to move in a vertical plane perpendicular to the magnetic meridian. The needle will stay in

Force between two identical bar magnets whose centres are $\mathrm{r}$ meter apart is $4.8 \mathrm{N}$ when their axes are in same line. If separation is increased to $2r$, the force between them is reduced to :

A coil in the shape of an equilateral triangle of side $l$ is suspended between the pole pieces of a permanent magnet, such that $\overrightarrow{B}$ is in plane of the coil. If due to current $I$ in the traingle, a torque $\overrightarrow{\tau }$ acts on it, the side $l$ of the triangle is

A frog can be levitated in magnetic field produced by a current in a vertical solenoid placed below the frog. This is possible because the body of the frog behave as

Assertion : A magnet may levitated above a superconducting material
Reason : There is always repulsive force between a diamagnet and a magnet! that produces non uniform magnetic field