In terms of basic units of mass $(M)$,length $(L)$,time $(T)$ and charge $(Q)$,the dimensions of magnetic permeability of vacuum $(\mu_0)$ would be

$A$ small cube of side $1 \ mm$ is placed at the center of a circular loop of radius $20 \ cm$. If the current in the loop is $2 \ A$,then the magnetic energy stored inside the cube is (Assume $\mu_0 = 4 \pi \times 10^{-7} \ SI$ units).

$A$ wire carrying current $I$ and another carrying $2I$ in the same direction produce a magnetic field $B$ at the midpoint. What will be the field when the $2I$ wire is switched off?

The adjoining figure shows a conductor carrying a current $i$. The magnetic field at the origin is

$A$ cylindrical conductor of radius $R$ carries a current $i$. The value of the magnetic field at a point which is $R/4$ distance inside from the surface is $10 \, T$. Find the value of the magnetic field at a point which is $4R$ distance outside from the surface.

An infinitely long straight conductor is bent into the shape as shown in the figure. It carries a current of $i$ $ampere$ and the radius of the circular loop is $r$ $metre$. Then the magnetic induction at its centre $O$ will be: