Magnetic Effects of Current Questions

A square loop $ABCD$ carrying a current $i$, is placed near and coplanar with a long straight conductor $XY$ carrying a current $I$. The net force on the loop will be:

A long straight wire of radius $a$ carries a steady current $I$. The current is uniformly distributed over its cross-section. The ratio of the magnetic fields $B$ and $B^{\prime }$, at radial distances $a/2$ and $2a$ respectively, from the axis of the wire is:

A long wire carrying a steady current is bent into a circular loop of one turn. The magnetic field at the centre is $B$. It is then bent into a circular coil of $n$ turns. The magnetic field at the centre of this coil will be:

An electron is moving in a circular path under the influence of a transverse magnetic field of $3.57\times 10^{-2}\text{T}$. If the value of $e/m$ is $1.76\times 10^{11}\text{C/kg}$, the frequency of revolution of the electron is: