A particle carrying a charge equal to $100$ times the charge on an electron is rotating per second in a circular path of radius $0.8$ $metre$. The value of the magnetic field produced at the centre will be $({\mu _0} = $ permeability for vacuum)

Magnetic effect of current was discovered by

Unit of magnetic permeability is

Two concentric coils $X$ and $Y$ of radii $16 \,\,cm$ and $10 \,\,cm$ lie in the same vertical plane containing $N-S$ direction. $X$ has $20$ $turns$ and carries $16 \,\,A.$ $Y$ has $25$ $turns$ $\&$ carries $18\,A$. $X$ has current in anticlockwise direction and $Y$ has current in clockwise direction for an observer, looking at the coils facing the west. The magnitude of net magnetic field at their common centre is

The unit vectors $\hat i,\;\hat j\;{\rm{and }}\,\hat k$ are as shown below. What will be the magnetic field at $O$ in the following figure

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