List the properties of magnetic field lines.
The properties of magnetic field lines are as follows:
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Magnetic field lines emerge from the north pole and merge at the south pole of a magnet. Inside the magnet, the direction of field lines is from its south pole to its north pole. Thus, the magnetic field lines are closed curves.
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The relative strength of the magnetic field is shown by the degree of closeness of the field lines. The field lines are closer together where the magnetic field is greater (stronger), and the force acting on a pole is greater where the field lines are crowded.
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No two field lines cross each other. If they did, it would mean that at the point of intersection, the compass needle would point towards two directions, which is not possible.
Explanation
The answer is derived directly from the textbook context which explains that field lines emerge from north and merge at south pole, forming closed curves. The context also states that the degree of closeness indicates field strength, and that field lines never intersect because that would imply two directions at one point, which is impossible for a compass needle.