When a certain length of wire is turned into one circular loop, the magnetic induction at the centre of coil due to some current flowing is ${B_1}$ If the same wire is turned into three loops to make a circular coil, the magnetic induction at the center of this coil for the same current will be

The fractional change in the magnetic field intensity at a distance $'r'$ from centre on the axis of current carrying coil of radius $'a'$ to the magnetic field intensity at the centre of the same coil is : (Take $r << a )$

In the figure, shown the magnetic induction at the centre of there $arc$ due to the current in portion $AB$ will be

The magnetic field at the centre of current carrying coil is

For adjoining fig., The magnetic field at point, $P$ will be

A straight wire carrying a current of $14\,A$ is bent into a semicircular are of radius $2.2\,cm$ as shown in the figure. The magnetic field produced by the current at the centre $(O)$ of the arc. is $.........\,\times 10^{-4}\, T$