At a distance of $10\, cm$ from a long straight wire carrying current,the magnetic field is $0.04\, T$. At a distance of $40\, cm$,the magnetic field will be....$T$

$A$ 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

$A$ steady current flows in a long wire. It is bent into a circular loop of one turn and the magnetic field at the centre of the coil is $B$. If the same wire is bent into a circular loop of $n$ turns, the magnetic field at the centre of the coil is

The magnetic field at the center of a circular coil of radius $0.1\, m$ having $1000$ turns and carrying a current of $0.1\, A$ is:

An infinitely long wire,located on the $z$-axis,carries a current $I$ along the $+z$-direction and produces the magnetic field $\vec{B}$. The magnitude of the line integral $\int \vec{B} \cdot d\vec{l}$ along a straight line from the point $(-\sqrt{3} a, a, 0)$ to $(a, a, 0)$ is given by [$\mu_0$ is the magnetic permeability of free space.]

$A$ negative charge is moving towards the observer. What will be the direction of the magnetic field produced by it,as seen by the observer?