The magnetic field due to a straight conductor of uniform cross-section of radius $a$ and carrying a steady current is represented by

$A$ coil having $N$ turns carries a current $I$ as shown in the figure. The magnetic field intensity at point $P$ is

Two parallel wires situated at a distance $2a$ are carrying equal currents $i$ in opposite directions as shown in the figure. The value of the magnetic field at a point $P$ situated at equal distances $r$ from both the wires will be:

$A$ current of $4 \ A$ is passed through a square loop of side $5 \ cm$ made of a uniform manganin wire as shown in the figure. The magnetic field at the centre of the loop is

The current through $ABC$ and $A'B'C'$ is $I$. What is the magnetic field at $P$? Given $BP = PB' = r$ (Here $C', B', P, B, C$ are collinear).

Which law is useful to determine the relation between current and the magnetic field produced by it?