Question

A magnetic lines of force inside a bar magnet
A. Are from North Pole to South Pole of the magnet
B. Do not exist
C. Depend upon the area of cross section of the bar magnet
D. Are from South Pole to North Pole of the magnet

Answer 1

Hint: Firstly, you could recall that magnetic field lines are just representations of the magnetic vector field. You may then recall the various properties of the magnetic field lines of force. One of the properties will give you the direction of the field lines inside a bar magnet.

Complete solution:
In the question, we are asked about the magnetic lines of force in the inside of a bar magnet.
Firstly, we should understand that magnetic lines of force are just imaginary lines that describe the pattern of the magnetic field. After understanding that the magnetic field lines of force actually don't exist, you could recall some of its properties.
You may recall that the magnetic field lines of force are actually known to be continuous. By continuous, it is meant that they form closed loops which have neither beginning nor end. Magnetic field lines are known to travel from its North Pole to the South Pole. But this is for the outside of the magnet. For the inside, in order for the magnetic field lines to form a closed loop, they have to be directed from the south to the north.
Therefore, we found that the magnetic lines of force inside a bar magnet are directed from the South Pole to the North Pole of the magnet.

Hence, option D is found to be the correct answer.

Note:
Some of the other properties of these field lines are:
1) The tangent to these field lines will give the direction of the magnetic field.
2) The closeness of these field lines defines the strength of the field.
3) No two magnetic field lines cross each other and thus we could say that the field is unique at any point in space.