Magnetic fields at two points on the axis of a circular coil at a distance of $0.05\, m$ and $0.2\, m$ from the centre are in the ratio $8: 1.$ The radius of coil is .......... $m$
$0.2$
$0.1$
$0.15$
$1.0$
Unit of magnetic permeability is
A straight section $PQ$ of a circuit lies along the $X$-axis from $x = - \frac{a}{2}$ to $x = \frac{a}{2}$ and carries a steady current $i$. The magnetic field due to the section $PQ$ at a point $X = + a$ will be
Two long straight wires are placed along $x$-axis and $y$-axis. They carry current $I_1$ and $I_2$ respectively. The equation of locus of zero magnetic induction in the magnetic field produced by them is
A straight wire of finite length carrying current $l$ subtends an angle of $60^{\circ}$ at point $P$ as shown. The magnetic field at $P$ is
In the given figure net magnetic field at $O$ will be