⚛️ Physics · Magnetism and Matter · NEET & JEE

A bar magnet has magnetic moment m and length 2l. It is cut into two equal halves with a cut perpendicular to its length, so each piece is half as long. The magnetic moment of each new piece is:

Answer: m/2.

A m
B m/2
C m/4
D 2m

Correct answer: B. m/2

Explanation: Cutting perpendicular to the axis halves the length while the pole strength stays the same, so the new magnetic moment of each piece is half the original moment.

Magnetic field lines of a bar magnet, emerging from the north pole and curving round to enter the south pole outside the magnet

Magnetic field of a bar magnet: field lines emerge from the north pole and re-enter at the south pole outside the magnet, forming continuous closed loops. Image: Geek3, CC BY-SA 3.0, via Wikimedia Commons.

Concept context

Bar magnets, Earth's magnetism, and how different materials respond to an external magnetic field - diamagnetic, paramagnetic, and ferromagnetic behaviour.

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A bar magnet has magnetic moment m and length 2l. It is cut into two equal halves with a cut perpendicular to its length, so each piece is half as long. The magnetic moment of each new piece is:

Concept context

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