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

A thin ring of radius 'R' metre has charge 'q' coulomb uniformly spread on it. The ring rotates about its axis with a constant frequency of 'f' revolution/s. The value of magnetic induction at the centre of the ring in $\text{Wb/m}^2$ is

( $\mu_0$ = permeability of free space )

When a resistance of $200\,\Omega$ is connected in series with a galvanometer of resistance G, its range is V. To triple its range, a resistance of $2000\,\Omega$ is connected in series. The value of G is

If a galvanometer is shunted by $\left(\dfrac{1}{n-1}\right)^{th}$ of the value of its resistance, then the fraction of the total current passing through the galvanometer is