Q 12-05-009NEETJEE MainEAMCET 2008 (Engineering)Medium
With a standard rectangular bar magnet, the time period of a vibration magnetometer is $4$ s. The bar magnet is cut parallel to its length into four equal pieces. The time period of the vibration magnetometer when one piece is used (in seconds) is (bar magnet breadth is small)
Answer: (C) $4$
Each piece has $\dfrac{1}{4}$ the mass and the same length, so $I' = \dfrac{I}{4}$. Its pole strength is also $\dfrac{1}{4}$, so $M' = \dfrac{M}{4}$.
$T = 2\pi\sqrt{\dfrac{I}{MB}}$ is unchanged: $4$ s.
Solution by Sreeraj P, M.Sc Physics