A proton moves along horizontal line and towards observer, the pattern of concentric circular field lines of magnetic field which produced due to its motion : 

An equilateral triangle of a side $a$ carries a current $I$. The magnetic field at a point $P$, which is the vertex of the triangle:

Two infinite length wires carry equal current and placed along x and y-axis respectively. At which points the resultant magnetic field is zero ?

For given current distribution, each infinite length wire produces magnetic field ’B’ at origin then resultant magnetic field at origin ’O’ is :-

A circular coil of one turn in formed by a$6.28 \mathrm{m}$ Length wire, which carries a current of $3.14 \mathrm{A}$. The magnetic field at the centre of coil is :-