An $\alpha$ particle is revolving in a circle of radius $r$ with frequency $f$. Find the value of its magnetic dipole moment.

Magnetic field at the centre of a circular loop of area $A$ is $B$. Then the magnetic moment of the loop is ($\mu_0$ is the permeability of free space).

$A$ ring of radius $R$,made of an insulating material,carries a charge $Q$ uniformly distributed on it. If the ring rotates about the axis passing through its centre and normal to the plane of the ring with a constant angular speed $\omega$,then the magnitude of the magnetic moment of the ring is:

$A$ charge $q$ is spread uniformly over an insulated loop of radius $r$. If it is rotated with an angular velocity $\omega$ with respect to the normal axis,then the magnetic moment of the loop is:

$A$ uniform conducting wire of length $12 a$ and resistance $R$ is wound up as a current-carrying coil in the shape of,
$(i)$ an equilateral triangle of side $a$.
$(ii)$ a square of side $a$.
The magnetic dipole moments of the coil in each case respectively are:

The magnetic moments associated with two closely wound circular coils $A$ and $B$ of radius $r_A = 10 \ cm$ and $r_B = 20 \ cm$ respectively are equal. If $N_A, I_A$ and $N_B, I_B$ are the number of turns and current of $A$ and $B$ respectively,then which of the following relations is correct?