If a current of $15 \,A$ passes through a solenoid of length $25 \,cm$,radius $2 \,cm$ and number of turns $500$,then the magnetic moment of the solenoid is

$A$ loop carrying current $I$ lies in the $x$-$y$ plane as shown in the figure. The unit vector $\hat{k}$ is coming out of the plane of the paper. The magnetic moment of the current loop 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:

Magnetic induction at the centre of a circular loop of area $\pi \ m^2$ is $0.1 \ T$. The magnetic moment of the loop is ( $\mu_0 = \text{permeability of air}$ ).

Two wires of the same length are shaped into a square and a circle. If they carry the same current,the ratio of their magnetic moments is:

An insulating rod of length $l$ carries a charge $q$ distributed uniformly on it. The rod is pivoted at an end and is rotated at a frequency $f$ about a fixed perpendicular axis. The magnetic moment of the system is