A square loop of side $2a,$ and carrying current $I$ is kept in $XZ$ plane with its centre at origin. A long wire carrying the same current $I$ is placed parallel to the $z$-axis and passing through the point $(0, b, 0),(b>> a)$. The magnitude of the torque on the loop about $z$-axis is given by.

In the diagram shown, I₁, I₂ are the magnitude of current in the square loop and infinite long straight conductor respectively. The net magnetic field at the centre of loop is zero, then

In the figure shown, there are two semicircles of radii $r_1$ and $r_2$ in which a current $i$ is flowing. The magnetic induction at the Centre $O$ will be

Find the magnetic field at point $\mathrm{P}$ due to a straight line segment $\mathrm{A}\mathrm{B}$ of length $6 \mathrm{c}\mathrm{m}$ carrying a current of $5 \mathrm{A}.$ (See figure) $\left({\mu }_0=4\pi \times {10}^{-7} {\mathrm{NA}}^{-2}\right)$