The ratio of the magnetic field and the magnetic moment at the centre of a current-carrying circular loop is $x$. When both the current and the radius are doubled,the ratio will be:

$A$ circular coil of radius $4\, cm$ and of $20$ turns carries a current of $3$ amperes. It is placed in a magnetic field of intensity $0.5\, Wb/m^2$. The magnetic dipole moment of the coil is.......$A \cdot m^2$.

$A$ wire of length $2 \, m$ carrying a current of $1 \, A$ is bent to form a circle. The magnetic moment of the coil is

The magnetic field at the centre of a current carrying circular coil of an area $A$ is $B$. The magnetic moment of the coil is (where $\mu_0$ is the permeability of free space).

An electron of charge $e$ moves in a circular orbit of radius $r$ around the nucleus at a frequency $v$. The magnetic moment associated with the orbital motion of the electron is

In an atom,an electron of charge $(-e)$ performs uniform circular motion ($U$.$C$.$M$.) around a stationary positively charged nucleus with a period of revolution $T$. If $r$ is the radius of the orbit of the electron and $v$ is the orbital velocity,then the circulating current $I$ is proportional to: