$A$ coil having $100$ turns is wound tightly in the form of a spiral with inner and outer radii $1 \text{ cm}$ and $2 \text{ cm}$, respectively. When a current $1 \text{ A}$ passes through the coil, the magnetic field at the centre of the coil is

Write the equation for the magnetic field due to a circular current-carrying loop at a point on the axis of the loop. Give its special cases.

$A$ current $I_0$ flows through a metallic circular loop of radius $r$. The resistance of the segment $ABC$ is half that of the segment $ADC$. The magnitude of the magnetic field at the centre $O$ of the loop is:

Which of the following statements is true regarding magnetic lines of force?

$A$ current loop $ABCD$ is held fixed on the plane of the paper as shown in the figure. The arcs $BC$ (radius $= b$) and $DA$ (radius $= a$) of the loop are joined by two straight wires $AB$ and $CD$. $A$ steady current $I$ is flowing in the loop. The angle made by $AB$ and $CD$ at the origin $O$ is $30^\circ$. Another straight thin wire with steady current $I_1$ flowing out of the plane of the paper is kept at the origin. The magnitude of the magnetic field $(B)$ due to the loop $ABCD$ at the origin $(O)$ is:

$A$ long straight wire carrying current $16 \,A$ is bent at $90^{\circ}$ such that one segment lies along the positive $x$-axis and the other segment lies along the positive $y$-axis. What is the magnitude of the magnetic field at the point $P(-2 \,mm, 0)$ (in $\,mT$)? (Assume $\frac{\mu_0}{4 \pi} = 10^{-7} \,T \cdot m/A$)