Time period for a magnet is T. If it is divided in four equal parts along its axis and perpendicular to its axis as shown then time period for each part will be

Options

A. 4T
B. T/4
C. T/2
D. T

Answer

C

Explanation

Pole strength `= (q_(m))/(2)`, length = l/2
`therefore M.= (q_(m))/(2).(l)/(2)= (M)/(4)`
Moment of inertia
`I.= (("mass")/(4) xx ((l)/(2))^(2))/(12)= (I)/(16)`
`T.= 2pi sqrt((I.)/(M.B_(H)))= 2pi sqrt((I//16)/((M//4)xx B))= (T)/(2)`