A closely wounded circular coil of radius $5\,cm$ produces a magnetic field of $37.68 \times 10^{-4}\,T$ at its center. The current through the coil is $......A$. [Given, number of turns in the coil is $100$ and $\pi=3.14]$

When equal current is passed through two coils, equal magnetic field is produced at their centres. If the ratio of number of turns in the coils is $8: 15$, then the ratio of their radii will be

the magnetic induction at $O$ due to the whole length of the conductor is

Give Oersted’s observation.

Two circular coils $1$ and $2$ are made from the same wire but the radius of the $1^{st}$ coil is twice that of the $2^{nd}$ coil. What is the ratio of potential difference in volts should be applied across them so that the magnetic field at their centres is the same?

The magnetic field at the center of current carrying circular loop is $B _{1}$. The magnetic field at a distance of $\sqrt{3}$ times radius of the given circular loop from the center on its axis is $B_{2}$. The value of $B_{1} / B_{2}$ will be.