Question

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 placed on top of P's North Pole
• C. Q is of unmagnetized ferromagnetic material
• D. Nothing can be said about Q's properties

Answer 1

Answer: (B)

Q is a bar magnet identical to P, and its north pole placed on top of P's North Pole

Answer 2

$T = 2 \pi \sqrt { \frac { I } { M B _ { H } } }$. If Q is an identical bar magnet then time period of system will be $T ^ { \prime } = 2 \pi \sqrt { \frac { 2 I } { ( 2 M ) B _ { H } } } = T$