$A$ straight wire of diameter $0.5\, mm$ carrying a current of $1\, A$ is replaced by another wire of $1\, mm$ diameter carrying the same current. The strength of the magnetic field at a point far away is

Two long parallel wires carrying currents $8 \text{ A}$ and $15 \text{ A}$ in opposite directions are placed at a distance of $7 \text{ cm}$ 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 magnetic field at $P$ is $X \times 10^{-6} \text{ T}$. Find $X$. (Given: $\sqrt{2} = 1.4, \mu_0 = 4\pi \times 10^{-7} \text{ SI unit}$)

The magnetic induction in air at a point $1\,cm$ away from a long straight wire that carries a current of $1\,A$ will be:

The magnetic field at the centre of a circular current-carrying conductor of radius $r$ is $B_{c}$. The magnetic field on its axis at a distance $r$ from the centre is $B_{a}$. The value of $B_{c} : B_{a}$ will be

$A$ current $i$ flows in a circular arc of wire of radius $R$,which subtends an angle of $3\pi / 2$ radians at its centre. The magnetic induction at the centre is

$A$ current $I$ flows in an infinitely long wire with a cross-section in the form of a semi-circular ring of radius $R$. The magnitude of the magnetic induction along its axis is: