$A$ current of $0.1\, A$ circulates around a coil of $100$ turns and having a radius equal to $5\, cm$. The magnetic field set up at the centre of the coil is $(\mu_0 = 4\pi \times 10^{-7} \, Wb/A \cdot m)$

In a hydrogen atom,an electron is revolving at $6.6 \times 10^{15} \text{ rev/s}$ around the nucleus in an orbit of radius $0.47 \text{ Å}$. The magnetic field induction produced at the centre of the orbit is nearly: (in $\text{ Wb m}^{-2}$)

Two coils $P$ and $Q$ each of radius $R$ carry currents $I$ and $\sqrt{8} I$ respectively in the same direction. These coils are lying in perpendicular planes such that they have a common centre. The magnitude of the magnetic field at the common centre of the two coils is ($\mu_0 =$ permeability of free space).

$\frac{V \cdot s}{A \cdot m}$ is the unit of which physical quantity?

Describe the arrangement of iron filings sprinkled around a straight current-carrying wire.

Current $I$ is flowing in a conductor shaped as shown in the figure. The radius of the curved part is $r$ and the length of the straight portions is very large. The value of the magnetic field at the centre $O$ will be