Q. Using a bar magnet $P$, a vibration magnetometer has time period $2seconds$. When a bar $Q$ (identical to $P$ in mass and size) is placed on top of $P$, the time period is unchanged. Which of the following statements is true
A) $Q$ is of non-magnetic material
B) $Q$ is a bar magnet identical to $P$, and its north pole is placed on top of $P'$s north pole
C) $Q$ is of unmagnetized ferromagnetic material
D) Nothing can be said about $Q$’s properties
Explanation
(b) $T = 2\pi\sqrt{\frac{1}{MB_{H}}}.$ If $Q$ is an identical bar magnet then time period of system will be $T^{'} = 2\pi\sqrt{\frac{2I}{(2M)B_{H}}} = T$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.