A circular current carrying coil has a radius $R$. The distance from the centre of the coil on the axis where the magnetic induction will be $\frac{1}{8}^{th}$ to its value at the centre of the coil, is
$\frac{R}{{\sqrt 3 }}$
$R\sqrt 3 $
$2\sqrt 3 \,R$
$\frac{2}{{\sqrt 3 }}R$
Magnetic effect of current was discovered by
A circular coil of wire consisting of $100$ turns, each of radius $8.0\; cm$ carries a current of $0.40\, A$. What is the magnitude of the magnetic field $B$ at the centre of the coil?
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
Two concentric circular coils of ten turns each are situated in the same plane. Their radii are $20$ and $40\, cm$ and they carry respectively $0.2$ and $0.3$ $ampere$ current in opposite direction. The magnetic field in $weber/{m^2}$ at the centre is
Write Biot-Savart law.