If the unit of magnetic flux is in weber,then the unit of magnetic field is . . . . . . .

Two concentric rings are kept in the same plane. The number of turns in each ring is $25$. Their radii are $50 \text{ cm}$ and $200 \text{ cm}$,and they carry electric currents of $0.1 \text{ A}$ and $0.2 \text{ A}$ respectively in mutually opposite directions. The magnitude of the magnetic field produced at their centre is . . . . . . $\text{T}$.

$A$ thin ring of radius $R$ carries a uniformly distributed charge. The ring rotates at a constant speed $N$ r.p.s. about its axis perpendicular to the plane. If $B$ is the magnetic field at the centre,the charge on the ring is ($\mu_0 =$ permeability of free space).

The magnetic field at the centre of a current-carrying circular coil is

The magnetic field intensity at the centre of a circular wire of radius $0.1 \,m$ carrying a current of $0.2 \,A$ is:

$A$ circular coil of radius $R$ carries an electric current. The magnetic field due to the coil at a point on the axis of the coil located at a distance $r$ from the centre of the coil,such that $r \gg R$,varies as: