A circular coil ‘$A$’ has a radius $R$ and the current flowing through it is $I$. Another circular coil ‘$B$’ has a radius $2R$ and if $2I$ is the current flowing through it, then the magnetic fields at the centre of the circular coil are in the ratio of (i.e.${B_A}$ to ${B_B}$)

Magnetic field intensity at the centre of coil of $50$ $turns$, radius $0.5\, m$ and carrying a current of $2\, A$ is

A long straight wire, carrying current $I$ is bent at its mid-point to form an angle of $45^{\circ}$. Induction of magnetic field (in tesla) at point $P$, distant $R$ from point of bending is equal to

The magnetic field on the axis of a circular loop of radius $100\,cm$ carrying current $I=\sqrt{2}\,A$, at point $1\,m$ away from the centre of the loop is given by

Give convection for electric or magnetic field emerging out of the plane of the paper and going into the plane of paper.

The magnetic field at the centre of a circular coil of radius $r$ carrying current $I$ is ${B_1}$. The field at the centre of another coil of radius $2 r$ carrying same current $I$ is ${B_2}$. The ratio $\frac{{{B_1}}}{{{B_2}}}$ is