Two infinite length wires are placed as shown in the figure. Find the magnitude of the magnetic field at point $M$,which is the midpoint of the line joining the two wires.

$A$ circular loop is kept in the vertical plane that contains the north-south direction. It carries a current that is towards the south at the topmost point. Let $A$ be a point on the axis of the circle to the east of it and $B$ be a point on this axis to the west of it. The magnetic field due to the loop is:

The magnetic effect of current was discovered by

An equilateral triangle of side '$a$' carries a current '$i$'. What is the magnetic field at point '$P$' (a vertex of the triangle)?

$B_{X}$ and $B_{Y}$ are the magnetic fields at the centre of two coils $X$ and $Y$ respectively,each carrying equal current. If coil $X$ has $200$ turns and $20 \ cm$ radius and coil $Y$ has $400$ turns and $20 \ cm$ radius,the ratio of $B_{X}$ and $B_{Y}$ is:

It is found that a non-zero current element is unable to produce any magnetic field at a particular point. Then the angle between the current element and the position vector of that point with respect to the current element is