A closed surface is drawn around the south pole of a bar magnet, so t…

The correct answer is Option (2) → zero, because as many field lines leave the surface as enter it

Magnetic field lines form continuous closed loops. Outside the magnet they go from the N-pole to the S-pole, and inside the magnet they go from the S-pole to the N-pole.

Option (1) inward, because the field lines outside the magnet converge into the south pole — Incorrect. Outside the magnet, lines do enter the surface near the south pole. The same lines then run on inside the magnet and leave the surface, so the inward flux is balanced.

Option (2) zero, because as many field lines leave the surface as enter it — Correct. Every line that enters the surface also leaves it. The net flux around the S-pole, as around the N-pole, is zero.

Option (3) outward, because the field lines inside the magnet go from the south pole to the north pole — Incorrect. Inside the magnet, lines do leave the surface. These are the same lines that entered it from outside, so the outward flux is balanced too.

Option (4) non-zero, and larger for a stronger magnet — Incorrect. A stronger magnet has more field lines. Each line still enters and leaves the surface once, so the net flux stays zero.

NCERT (2026-27):
Example 5.3 – “(e) Right. These are field lines outside and inside a bar magnet. Note carefully the direction of field lines inside. Not all field lines emanate out of a north pole (or converge into a south pole). Around both the N-pole, and the S-pole, the net flux of the field is zero.”

Magnetism and Gauss’s Law – “The net magnetic flux through any closed surface is zero.”