A circular current carrying coil has radius $$R$$. The magnetic induction at the centre of the coil is $$B_C$$. The magnetic induction of the coil at a distance $$\sqrt{3} R$$ from the centre along the axis is $$B_A$$. The ratio $$B_A: B_C$$ is

A circular coil of radius '$$r$$' and number of turns ' $n$ ' carries a current '$$I$$'. The magnetic fields at a small distance '$$h$$' along the axis of the coil $$\left(B_a\right)$$ and at the centre of the coil $$\left(\mathrm{B}_{\mathrm{c}}\right)$$ are measured. The relation between $$B_c$$ and $$B_a$$ is

Two concentric circular coils A and B have radii $$20 \mathrm{~cm}$$ and $$10 \mathrm{~cm}$$ respectively lie in the same plane. The current in coil A is $$0.5 \mathrm{~A}$$ in anticlockwise direction. The current in coil B so that net field at the common centre is zero, is

Two concentric circular coils of 10 turns each are situated in the same plane. Their radii are $$20 \mathrm{~cm}$$ and $$40 \mathrm{~cm}$$ and they carry respectively $$0.2 \mathrm{~A}$$ and $$0.3 \mathrm{~A}$$ current in opposite direction. The magnetic field at the centre is ($$\mu_0=4 \pi \times 10^{-7}$$ SI units)