Two concentric co-planar coils of turns $n_1$ and $n_2$ have radii ratio $2:1$, respectively. Equal currents in both the coils flow in opposite directions. If net magnetic field is zero at their common centre, then $n_1:n_2$ is,

Find out magnetic field at point $O$ for the following current distributions.

Find out magnetic field at point $O$ for the following current distributions.

A conducting rod moves towards right with constant velocity $v$ in uniform transverse magnetic field. Graph between force applied by the external agent v/s velocity and power supplied by the external agent v/s velocity:
  

 If $5 \mathrm{A}$ current is flowing in this system and the diameter of the loop is$10 \mathrm{cm}$, then find magnetic field at point $O$ due to given current distribution.

The figure shows a circular loop with radius $r$. The resistance of arc $ABC$ is $5 \mathrm{\Omega }$ and that of $ADC$ is $10 \mathrm{\Omega }$. The magnetic field at the centre of the loop is,