Question

What are the magnetic field lines?list two characteristic properties of these lines?

Answer 1

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. 
Properties:
1. They seek the path of least resistance between opposite magnetic poles.
2. They never cross one another.
3. They all have the same strength.

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Answer 2

Magnetic field lines are the lines drawn in a magnetic field along which north magnetic pole would move. The direction of a magnetic field at a point is determined with the help of a small magnetic compass. When a compass is moved along the magnetic line, then the line drawn from the south pole of the compass to its north pole indicates the direction of the magnetic field.

Properties of magnetic lines of force:

(i) The magnetic lines originate from the north pole and end at the south pole.

(ii) The magnetic field lines of a magnet form a continuous closed loop.

(iii) The magnetic lines of force do not intersect each other.

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