The magnetic field intensity at the centre of a circular wire of radius $0.1 \,m$ carrying a current of $0.2 \,A$ is:

$A$ current of $5 \; A$ flows through a square loop of side length $\frac{1}{\sqrt{2}} \; m$. The magnitude of the magnetic field $B$ at the centre of the square loop is $p \times 10^{-6} \; T$. Find the value of $p$. [Take $\mu_0 = 4 \pi \times 10^{-7} \; T \cdot m \cdot A^{-1}$].

Two concentric circular coils of ten turns each are situated in the same plane. Their radii are $20 \ cm$ and $40 \ cm$ and they carry respectively $0.2 \ A$ and $0.3 \ A$ current in opposite directions. The magnetic field in $Wb/m^2$ at the centre is:

$A$ small current element of length $d\ell$ carrying current $I$ is placed at $(1, 1, 0)$ and is carrying current in the $+z$ direction. If the magnetic field at the origin is $\vec{B}_1$ and at the point $(2, 2, 0)$ is $\vec{B}_2$,then:

As shown in the figure,a current of $2\,A$ flows in an equilateral triangle of side $4 \sqrt{3}\,cm$. The magnetic field at the centroid $O$ of the triangle is:
(Neglect the effect of the earth's magnetic field.)

Two identical long current-carrying wires are bent into the shapes shown in the figures. If the magnitudes of the magnetic fields at the centers $P$ and $Q$ of the quarter-circular arcs are $B_1$ and $B_2$ respectively, then the ratio $\frac{B_1}{B_2}$ is: