⚛️ Physics · Magnetism and Matter · NEET & JEE

In a vibration magnetometer the time period is 3 s. If the magnetic moment of the needle is doubled while the field is unchanged, the new period is:

Answer: 2.12 s.

A 6 s
B 3 s
C 2.12 s
D 1.5 s

Correct answer: C. 2.12 s

Explanation: T = 2π√(I/mB), so T is inversely proportional to √m. Doubling m gives T' = 3/√2 ≈ 2.12 s.

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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In a vibration magnetometer the time period is 3 s. If the magnetic moment of the needle is doubled while the field is unchanged, the new period is:

Concept context

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