$A$ long straight wire carries a current of $\pi \, A$. The magnetic field due to it will be $5 \times 10^{-5} \, Wb/m^2$ at what distance from the wire? $[\mu_0 = \text{permeability of free space}]$

An electron revolves in a circle of radius $0.4 \text{ Å}$ with a speed of $10^6 \text{ m/s}$ in a hydrogen atom. The magnetic field produced at the centre of the orbit due to the motion of the electron (in Tesla) is: $\left[\mu_0 = 4\pi \times 10^{-7} \text{ H/m}, q = 1.6 \times 10^{-19} \text{ C}\right]$

On connecting a battery to the two corners of a diagonal of a square conductor frame of side $a$,the magnitude of the magnetic field at the centre will be:

$A$ long wire carrying a steady current is bent into a circle of single turn. The magnetic field at the centre of the coil is $B$. If it is bent into a circular loop of radius $r_1$ having $n$ turns,the magnetic field at the centre of the coil for the same current is:

$A$ thin wire of length $l$ is carrying a constant current $i$. The wire is bent to form a circular coil. If the radius of the coil,thus formed,is $R$ and the number of turns in it is $n$,then which of the following graphs represents the variation of magnetic field induction $B$ at the centre of the coil?

$B_{x}$ and $B_{y}$ are the magnetic fields at the center of two coils $x$ and $y$ respectively,each carrying equal current. If coil $x$ has $200$ turns and $20 \ cm$ radius,and coil $y$ has $400$ turns and $20 \ cm$ radius,the ratio of $B_{x}$ and $B_{y}$ is $:-$