In bio savart law direction of magnetic field is shown by $d\vec B = \frac{{{\mu _0}}}{{4\pi }}\frac{{I\overrightarrow {dl}  \times \vec r}}{{{r^3}}}$

The earth's magnetic induction at a certain point is $7 \times {10^{ - 5}}\,Wb/{m^2}.$ This is to be annulled by the magnetic induction at the centre of a circular conducting loop of radius $5 \,cm$. The required current in the loop is......$A$

In the figure shown there are two semicircles of radii ${r_1}$ and ${r_2}$ in which a current $i$ is flowing. The magnetic induction at the centre $O$ will be

A long straight wire, carrying current $I,$ is bent at its midpoint to from an angle of $45^o.$ Induction of magnetic field at point $P,$ distant $R$ from point of bending is equal to :

A cell is connected between two points of a uniformly thick circular conductor. The magnetic field at the centre of the loop will be

In figure two parallel infinitely long current carrying wires are shown. If resultant magnetic field at point $A$ is zero. Then determine current $I.$ (in $A$)