Question

Write two properties of magnetic field lines.

Answer 1

Hint
We know that magnetic field lines are a visual tool used to represent magnetic fields. They describe the direction of the magnetic force on a north monopole at any given position. In the case of a magnetic field, since no isolated unit pole has ever been discovered, the field lines are called lines of force only in the sense that a small magnet is forced to align itself in the direction of these field lines. An electric charge traveling along a magnetic field line undergoes no magnetic force. Magnetic field lines are a visual tool used to represent magnetic fields. They describe the direction of the magnetic force on a north monopole at any given position. One useful analogy is the close connection between magnetic monopoles and electric charges

Complete step by step answer
So here are main two properties of magnetic field lines:
Magnetic field lines emerge from the north pole and merge at the south pole. As the distance between the poles increases, the density of magnetic lines decreases.
The direction of field lines inside the magnet is from the South Pole to the North Pole. Magnetic lines do not intersect with each other. The strength of the magnetic lines is the same throughout and is proportional to how close the lines are.
Here is the main diagram which will explain the magnetic field lines around a bar magnet.

Note
Thus, we can say that the closer the lines, the stronger the magnetic field (so the magnetic field from a bar magnet is strongest closest to the poles) the lines have arrowheads to show the direction of the force exerted by a magnetic north pole. Since the earth is a huge magnet with a magnetic north and south pole, the lines of magnetic force around the earth look like there is a huge vertical bar magnet running through the center of the earth. There is no known material that blocks magnetic fields without itself being attracted to the magnetic force. Magnetic fields can only be redirected, not created or removed. To do this, high-permeability shielding alloys are used. The magnetic field lines are strongly attracted into the shielding material.