What is the magnetic field at a distance $R$ from a coil of radius $r$ carrying current $I$ along its axis?

According to the Biot-Savart law,what is the magnetic field at a point on the axis of a current-carrying wire?

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.]

$A$ $10 \ A$ current is passing through a very long wire of radius $5 \ cm$. The magnetic field at a distance of $2 \ cm$ inside from its curved surface is . . . . . . $\times 10^{-5} \ T$.

What is the ratio of the magnetic field at the center of a circular ring of radius $R$ to the magnetic field at a point on its axis at a distance of $3R$ from the center?

$A$ cylindrical conductor of radius $R$ carries a current $i$. The value of the magnetic field at a point which is $R/4$ distance inside from the surface is $10 \, T$. Find the value of the magnetic field at a point which is $4R$ distance outside from the surface.