question_answer 52)

  A magnetic compass needle is placed in the plane of paper near point A as shown in figure .In which plane should astraight 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:

                    The straight current carrying conductor should be placed in the plane of paper so that it passes through A. This produces magnetic field in a plane perpendicular to plane of paper. The compass needle remains undetected due to vertical magnetic field produced by wire since compass needle are free to rotate only in horizontal plane. The deflection in compass needle is maximum when the conductor through A is perpendicular to the plane of paper and the magnetic field due to straight current conductor lies in the plane of paper.