Question

A magnetic compass needle is placed in the plane of paper near point A as shown in Figure. In which plane should a straight current carrying conductor be placed so that it passes through A and there is no change in the deflection of the compass? Under what condition is the deflection maximum and why?

Answer 1

We know that when the magnetic field and the direction of the current are perpendicular to each other, the deflection is maximum. But when they are on the same plane, no deflection takes place.

If we place the current-carrying conductor in the plane of paper such that it passes through A then, the field produced by it is perpendicular to the plane of paper and parallel to the vertical axis of the compass needle. As a result, there will be no deflection of the compass needle.

The deflection in the compass needle will be maximum when the conductor passes through A and is perpendicular to the plane of the paper.