$A$ magnetic field of $5 \times 10^{-5} \,T$ is produced at a perpendicular distance of $0.2 \,m$ from a long straight wire carrying electric current. If the permeability of free space is $4 \pi \times 10^{-7} \,T \cdot m/A$, the current passing through the wire in $A$ is:

$A$ horizontal overhead powerline is at a height of $5 \,m$ from the ground and carries a current of $150 \,A$ from East to West. The magnetic field directly below it on the ground is

$A$ circular loop of radius $0.0157\,m$ carries a current of $2.0\,A$. The magnetic field at the centre of the loop is $(\mu_0 = 4\pi \times 10^{-7}\,T\cdot m/A)$.

Two identical long conducting wires $AOB$ and $COD$ are placed at a right angle to each other,with one above the other such that $O$ is their common point. The wires carry currents $I_1$ and $I_2$,respectively. Point $P$ lies at a distance $d$ from $O$ along a direction perpendicular to the plane containing the wires. The magnetic field at point $P$ will be:

$A$ long wire is bent into a circular coil of one turn and then into a circular coil of smaller radius having $n$ turns. If the same current is passed in both the cases, the ratio of magnetic field produced at the centre for one turn to that of $n$ turns is

Two similar coils of radius $R$ are lying concentrically with their planes at right angles to each other. The currents flowing in them are $I$ and $2I$,respectively. The resultant magnetic field induction at the centre will be