Question

Are the magnetic field lines closed? Explain.

Answer 1

Hint : Magnetic field lines are basically continuous lines without the beginning or the end. They go from i.e., they move in a direction from the north pole to the south pole. They are different from electric field lines as the electric field lines begin on the positive charges and ends on the negative charges.

Complete step by step solution:
Magnetic field lines are closed curves as they propagate from the North pole outside the magnet's body to the magnet's body and from the south pole to the north pole inside the magnet's body.
Hence, the magnetic field lines are closed.

Additional Information: The field lines appear to be closed loops, but you cannot conclude that the lines are closed or open by looking at the picture of the field lines because we do not know about the alignment of the lines passing through the bar magnet. The direction of a magnetic line at a point gives the direction of the magnetic force at the north pole placed at that point. Since the direction of the magnetic field line is the direction of the force at the north pole. Therefore magnetic lines always start at the 'N' pole of the magnet and end at the magnet's lines S 'pole. However the magnetic lines inside the magnet range from the S-pole of the magnet to the N-pole of the magnet. Thus the magnetic field lines are closed.

Note: The properties of the magnetic field lines are as follows:
1. The field is always in a tangent position to the magnetic field line.
2. The magnetic field lines cannot ever cross each other.
3. They are continuous loops moving from the north pole to the south pole.
4. The magnetic field strength is directly proportional to the line density.