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

The magnetic field due to a current-carrying square loop of side $a$ at a point located symmetrically at a distance of $a/2$ from its centre (as shown in the figure) is:

Consider a tightly wound $100$ turn coil of radius $10 \; cm$,carrying a current of $1 \; A$. What is the magnitude of the magnetic field at the centre of the coil?

$A$ circular current-carrying coil has a radius $R$. The distance from the centre of the coil on the axis where the magnetic induction will be $\frac{1}{8}$th of its value at the centre of the coil is:

$A$ thin wire of length $l$ is carrying a constant current $i$. The wire is bent to form a circular coil. If the radius of the coil,thus formed,is $R$ and the number of turns in it is $n$,then which of the following graphs represents the variation of magnetic field induction $B$ at the centre of the coil?

$A$ current flows through a circular coil of radius $R$. Find the distance from the center on the axis where the magnetic field is $\frac{1}{8}$th of the magnetic field at the center.