A circular loop placed in a plane perpendicular to the plane of paper carries a current when the key is ON. The current as seen from points A and B (in the plane of paper and on the axis of the coil) is anticlockwise and clockwise respectively. The magnetic field lines point from B to A. The N-pole of the resultant magnet is on the face close to
(a) A
(b) B
(c) A if the current is small, and B if the current is large
(d) B if the current is small and A if the current is large
Answer: A
Solution:
The magnetic field lines forms close loop, but if we see any magnet then magnetic field lines seems to originate from North Pole.
Within the magnet the magnetic field lines will be from South pole to North Pole.
As in this question, the magnetic field lines point from B to A. It means for outside world it is coming out from A.
Hence point A will be North Pole and point B will be South Pole.
The nature of face whether it will be South Pole or fool North Pole depends on the sense of current in the loop. This nature
does not depend on the magnitude of current.
Hence the correct option of this question is option A