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.

The electric current in a circular coil of $2$ turns produces a magnetic induction $B _{1}$ at its centre. The coil is unwound and is rewound into a circular coil of $5$ turns and the same current produces a magnetic induction $B _{2}$ at its centre.The ratio of $\frac{ B _{2}}{ B _{1}}$ is.

A charge $q$ coulomb moves in a circle at $n$ revolutions per second and the radius of the circle is $r$ metre; then magnetic field at the centre of the circle is

Charge $q$ is uniformly spread on a thin ring of radius $R.$ The ring rotates about its axis with a uniform frequency $f\, Hz.$ The magnitude of magnetic induction at the center of the ring is

The ratio of the magnetic field at the centre of a current carrying coil of the radius $a$ and at a distance ‘$a$’ from centre of the coil and perpendicular to the axis of coil is

Current $i$ is passed as shown in diagram. If radius of the circle is a, then the magnetic flux density at the centre $P$ will be: