Two identical long conducting wires $AOB$ and $COD$ are placed at right angle to each other with one above other such that $O$ is the common point for the two. The wires carry $I_1$ and $I_2$ currents, respectively. Point $P$ is lying at distance $d$ from $O$ along a direction perpendicular to the plane containing the wires. The magnetic field at the point $P$ will be,

A current of $0.1 \mathrm{A}$ circulates around a coil of $100$ turns and has a radius equal to $5 \mathrm{cm}$. The magnetic field set up at the centre of the coil is $\left({\mu }_0=4\pi \times {10}^{-7}\right.\mathrm{Wb} {\mathrm{A}}^{-1} {\mathrm{m}}^{-1}$$)$, 

A long straight wire is turned into a loop of radius $10 \mathrm{cm}$ (see figure). If a current of $8 \mathrm{A}$ is passed through the loop, then the value of the magnetic field and its direction at the centre $C$ of the loop shall be close to,