The magnitude of the force per unit length acting on a thin wire carrying a current $I=8 \text{ A}$ at a point $O$, if the wire is bent as shown in the figure with a radius $R=10 \pi \text{ cm}$, is (in $\mu \text{N/m}$)

$A$ coil having $2000$ turns is wound tightly in the form of a spiral with inner and outer radii $1 \,cm$ and $3 \,cm$, respectively. When a current $\frac{1}{\pi} \,mA$ passes through the coil, the magnetic field at the centre is calculated to be $K \ln 3 \times 10^{-6} \,T$. The value of $K$ is

Two infinite length wires are placed as shown in the figure. Find the magnitude of the magnetic field at point $M$,which is the midpoint of the line joining the two wires.

$A$ long straight wire of circular cross-section is made of a non-magnetic material. The wire is of radius $a$. The wire carries a current $I$ which is uniformly distributed over its cross-section. The energy stored per unit length in the magnetic field contained within the wire is

$A$ current of $1.5 \, A$ is flowing through an equilateral triangle of side $9 \, cm$. The magnetic field at the centroid of the triangle is (Assume that the current is flowing in the clockwise direction.)

Find the magnetic induction at point $O$ in the given figure.