The unit of magnetic permeability is

Two concentric circular coils of ten turns each are situated in the same plane. Their radii are $20 \ cm$ and $40 \ cm$ and they carry respectively $0.2 \ A$ and $0.3 \ A$ current in opposite directions. The magnetic field in $Wb/m^2$ at the centre is:

Magnetic field intensity $H$ at the centre of a circular loop of radius $r$ carrying current $I$ in e.m.u. is

Two concentric coils each of radius equal to $4 \pi \text{ cm}$ are placed at right angles to each other. If $10 \text{ A}$ and $24 \text{ A}$ are the currents flowing through the coils,respectively,the magnetic induction at the center of the coils will be

Two infinitely long wires are placed at $(1 \text{ cm}, 1 \text{ cm})$ and $(1 \text{ cm}, -1 \text{ cm})$ with $1 \text{ A}$ current in each and in the same directions perpendicular to the $xy$-plane. Let the magnetic field due to these current-carrying wires at the origin be $B$. If $B_0$ is the magnitude of the field if only one of them was present,then $\frac{|B|}{B_0}$ is

Magnetic field induction at the centre of a circular coil of radius $5 \,cm$ and carrying a current $0.9 \,A$ is (in $SI$ units) (where $\varepsilon_0$ is the absolute permittivity of air in $SI$ units,and the velocity of light $c = 3 \times 10^8 \,ms^{-1}$)