$A$ long wire is bent into a circular coil of one turn and then into a circular coil of smaller radius having $n$ turns. If the same current passes in both the cases,the ratio of magnetic fields produced at the centre for one turn to that of $n$ turns is

Two straight infinitely long current-carrying wires are kept along the $z-$axis at the coordinates $(0, a, 0)$ and $(0, -a, 0)$ respectively, as shown in the figure. The current in each wire is equal and directed along the negative $z-$axis (into the plane of the paper). The variation of the magnetic field on the $x-$axis will be approximately:

The magnetic field at the centre of a circular coil of radius $r$,through which a current $I$ flows,is:

$A$ current $I=5 \text{ A}$ flows along a thin wire shaped as shown in the figure. The radius of the curved part of the wire is $R=100 \text{ mm}$, and the angle $2\phi=90^{\circ}$. The magnitude of the magnetic field at point $O$ is approximately:
$\left[\text{Use, } \frac{\mu_0}{4\pi}=10^{-7} \text{ T m A}^{-1}\right]$ (in $\mu\text{T}$)

It is found that a non-zero current element is unable to produce any magnetic field at a particular point. Then the angle between the current element and the position vector of that point with respect to the current element is

Describe and illustrate the magnetic field lines produced by a current-carrying circular loop.