Question

The magnetic lines of force inside a bar magnet:
A. are from north-pole to south-pole of the magnet
B. do not exist
C. depends upon the area of cross-section of the bar magnet
D. are from south-pole to north-pole of the magnet

Answer 1

Hint: The magnetic forces around the area of a magnet is known as a magnetic field. In a bar magnet, the magnetic fields are strongest at either pole of the magnet. It is also equally strong at the north pole when compared with the south pole. At the center of the magnet and in between the poles and in the center, the force is weaker.

Complete step by step solution:
General properties of magnetic field lines:
1. The magnetic lines of force always form closed loops.
2. When moving from an area of higher permeability to an area of lower permeability the field lines tend to bulge out i.e. when moving from the surface of the magnet (poles) to the air density of the field line decreases.
3. Each and every field line has the same strength.
4. They never cross each other.
5. By convention, these field lines seem to originate from the north pole (N) & end into the south pole (S) of a bar magnet.
6. The direction inverses inside the magnet i.e. they appear to move from the south pole (S) towards the north pole (N).

$\therefore$ The magnetic lines of forces inside a bar magnet are from south-pole to north-pole of the magnet. Thus, the option (D) is correct.

Note:
The magnetic field lines are almost parallel to each other, as the bar magnet is made up of uniform ferromagnetic material with constant permeability throughout its length & bulge out as the lines move opposite to the poles & pass through air. Inside the bar magnet, the magnetic lines are continuing their journey to the opposite end.