Identify the correct properties of magnetic field lines.
(A) Magnetic field lines are directed from the south pole to the north pole outside the magnet.
(B) The magnetic field lines never intersect each other.
(C) Magnetic lines always form a closed and continuous curve.
(D) If magnetic field lines are parallel, then the magnetic field must be uniform throughout.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (B) and (C) only
(A) Magnetic field lines are directed from the south pole to the north pole outside the magnet. — Incorrect. Outside a magnet the lines run from the north pole to the south pole; they run from south to north only inside the magnet.
(B) The magnetic field lines never intersect each other. — Correct. At a point of intersection the field would have two directions, which is impossible.
(C) Magnetic lines always form a closed and continuous curve. — Correct. Magnetic monopoles do not exist, so the lines have no beginning or end and form closed loops.
(D) If magnetic field lines are parallel, then the magnetic field must be uniform throughout. — Incorrect. Parallel lines can be crowded closer in one place than in another, and then the field strength changes from place to place.
NCERT (2026-27):
The Magnetic Field Lines – “… (i) The magnetic field lines of a magnet (or a solenoid) form continuous closed loops.”
The Magnetic Field Lines – “… (iii) The larger the number of field lines crossing per unit area, the stronger is the magnitude of the magnetic field B.”
The Magnetic Field Lines – “… (iv) The magnetic field lines do not intersect, for if they did, the direction of the magnetic field would not be unique at the point of intersection.”