In a bar magnet, the magnetic field lines

The correct answer is Option (2) → form closed continuous curves, directed from north to south outside the magnet and from south to north inside the magnet

The tangent to a magnetic field line at a point gives the direction of \( \vec{B} \) there. Isolated magnetic poles do not exist. So the field lines of a magnet have no starting or end point. They form continuous closed loops.

Option (1) originate from the north pole and terminate at the south pole — Incorrect. Lines that begin and end belong to an electric dipole, where they start on the positive charge and end on the negative charge. Magnetic lines do not stop at the south pole. They continue through the magnet.

Option (2) form closed continuous curves, directed from north to south outside the magnet and from south to north inside the magnet — Correct. Outside the magnet the lines leave the north pole and curve round to the south pole. Inside the magnet they run from the south pole back to the north pole. So each line closes on itself.

Option (3) go from one pole to the other only outside the magnet — Incorrect. The field lines also pass through the body of the magnet. Without the part inside, they could not form closed loops.

Option (4) emerge radially outward from both poles — Incorrect. The lines come out of the north pole but go into the south pole. So at the south pole the field points into the magnet.

NCERT (2026-27):
The Magnetic Field Lines – “(i) The magnetic field lines of a magnet (or a solenoid) form continuous closed loops. This is unlike the electric dipole where these field lines begin from a positive charge and end on the negative charge or escape to infinity.”

Fig. 5.2: The field lines of (a) a bar magnet.