$A$ part of a long wire carrying a current $i$ is bent into a circle of radius $r$ as shown in the figure. The net magnetic field at the centre $O$ of the circular loop is

Two very long straight conductors (wires) are set parallel to each other. Each carries a current $I$ in the same direction and the separation between them is $2r$. The intensity of the magnetic field at point $P$ (as shown in the figure) ($\mu_0=$ permeability of free space) is

Two identical long parallel wires carry currents $I_1$ and $I_2$ such that $I_1 > I_2$. When the currents are in the same direction,the magnetic field at a point midway between the wires is $8 \times 10^{-6} \ T$. If the direction of $I_2$ is reversed,the field becomes $3.2 \times 10^{-5} \ T$. The ratio of $I_2$ to $I_1$ is

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

$A$ conducting wire is in the shape of a regular hexagon which is inscribed inside an imaginary circle of radius $R$. If a current $I$ flows through the wire, the magnitude of the magnetic field at the centre of the circle is

$A$ regular polygon of $6$ sides is formed by bending a wire of length $4 \pi \text{ m}$. If an electric current of $4 \pi \sqrt{3} \text{ A}$ is flowing through the sides of the polygon,the magnetic field at the centre of the polygon would be $x \times 10^{-7} \text{ T}$. The value of $x$ is . . . . . . .