The current associated with an electron of charge $e$ moving in a circular orbit of radius $r$ with speed $v$ around the positively charged nucleus is given by

Two concentric circular loops of radii $r_{1} = 30 \, cm$ and $r_{2} = 50 \, cm$ are placed in the $X-Y$ plane as shown in the figure. $A$ current $I = 7 \, A$ flows through them in the directions shown. The net magnetic moment of this system of two circular loops is approximately:

$A$ current carrying wire of length $L$ is transformed into a coil of $N$ turns. To achieve maximum magnetic moment,the coil

The magnetic field at the centre of a current carrying circular coil of area $A$ is $B$. The magnetic moment $(M)$ of the coil is $(\mu_0 = \text{permeability of free space})$

Two wires of same length are bent to form a circular loop with two turns and a square loop of one turn. Both of them carry the same current. The ratio of the magnetic moment of the circular loop of two turns to that of the square loop is

The ratio of the magnetic field at the centre of a current-carrying circular coil to its magnetic moment is $\alpha$. If the current and radius both are doubled,then the new ratio will become: