The ratio of the magnetic field at the centre of a circular ring of radius $R$ to the magnetic field at a point on its axis at a distance $2\sqrt{2}R$ from its centre is . . . . . .

$A$ solenoid of $1000$ turns per metre has a core with relative permeability $500$. Insulated windings of the solenoid carry an electric current of $5 \, A$. The magnetic flux density produced by the solenoid is (permeability of free space $= 4 \pi \times 10^{-7} \, H/m$)

$A$ closely wound flat circular coil of $25$ turns of wire has a diameter of $10\, cm$ and carries a current of $4\, A$. Determine the magnetic flux density at the centre of the coil.

$A$ very long conducting wire is bent in a semicircular shape from $A$ to $B$ as shown in the figure. The magnetic field at point $P$ for the steady current configuration is given by:

Do two magnetic field lines intersect each other? Why?

Two long parallel wires carrying currents $8\,A$ and $15\,A$ in opposite directions are placed at a distance of $7\,cm$ from each other. $A$ point $P$ is equidistant from both the wires such that the lines joining the point $P$ to the wires are perpendicular to each other. The magnitude of magnetic field at $P$ is $............\times 10^{-6}\,T$. (Given : $\sqrt{2}=1.4$)