The magnetic field at a distance $r$ from a long straight wire carrying current $i$ is $0.4 \ T$. The magnetic field at a distance $2r$ is: (in $T$)

$A$ circular current-carrying coil has radius $R$. At what distance from the centre of the coil on the axis,the magnetic induction will become $\frac{1}{8}$ th of its value at the centre of the coil?

$A$ magnetic field of $5 \times 10^{-5} \,T$ is produced at a perpendicular distance of $0.2 \,m$ from a long straight wire carrying electric current. If the permeability of free space is $4 \pi \times 10^{-7} \,T \cdot m/A$, the current passing through the wire in $A$ is:

The magnetic induction at the centre $O$ of the current-carrying bent wire shown in the adjoining figure is:

$A$ current $i$ is flowing through the loop. The direction of the current and the shape of the loop are as shown in the figure. The magnetic field at the centre $M$ of the loop is $\frac{\mu_{0} i}{R}$ times
$(MA=R, MB=2 R, \angle DMA=90^{\circ})$

Discuss the similarities and differences between the Biot-Savart law and Coulomb's law.