question_answer

Two identical bar magnets are placed on above  the other such that they are mutually perpendicular and bisect each other. The time period of this combination in a horizontal magnetic field is T. The time period of each magnet in the same field is                                       [CPMT 2005]

A)          \[\sqrt{2}\,T\]                

B)          \[{{2}^{\frac{1}{4}}}T\]

C)          \[{{2}^{-\frac{1}{4}}}T\]   

D)          \[{{2}^{-\frac{1}{2}}}T\]

Correct Answer: C

Solution :

           Time period of combination \[T=2\pi \sqrt{\frac{2I}{\sqrt{2}\,M.H}}\]                     ?..(i)                                 and time period of each magnet                    \[{T}'=2\pi \sqrt{\frac{I}{MH}}\]                   ??(ii)                    from (i) and (ii)  we get                                                                    \[{T}'=\frac{T}{{{2}^{1/4}}}={{2}^{-1/4}}T\]