Which of the following is NOT true about magnetic field lines?

The correct answer is Option (3) → Magnetic field lines begin at the south pole and terminate at the north pole.

Option (1) The magnetic field lines form closed loops. — True. The field lines of a magnet or a solenoid form continuous closed loops. They run from north to south outside the magnet and from south to north inside it.

Option (2) If a bar magnet is cut in half so that the north pole is on one piece and the south pole on the other, we still do not get two isolated magnetic poles. — True. Each half becomes a complete, weaker magnet with its own north and south pole, because isolated magnetic poles (monopoles) do not exist.

Option (3) Magnetic field lines begin at the south pole and terminate at the north pole. — Not true. Magnetic field lines neither begin nor end anywhere. Lines that start and stop belong to an electric dipole. There they begin on the positive charge and end on the negative charge. The lines of a magnet close on themselves.

Option (4) It is possible to make magnets out of iron and its alloys. — True. Iron is ferromagnetic, and alloys of iron such as alnico keep their magnetisation and are used for permanent magnets.

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.”