JEE Main & Advanced Physics Magnetism Question Bank Magnetic Equipments

  • question_answer
    At a certain place a magnet makes 30 oscillations per minute. At another place where the magnetic field is double, its time period will be                                                           [MP PMT 1989; MP PET/PMT 1988]

    A)            4 sec                                        

    B)            2 sec

    C)            \[\frac{1}{2}\sec \]            

    D)            \[\sqrt{2}\sec \]

    Correct Answer: D

    Solution :

               \[T=2\pi \sqrt{\frac{I}{M{{B}_{H}}}};\ \therefore \frac{{{T}_{1}}}{{{T}_{2}}}=\sqrt{\frac{{{({{B}_{H}})}_{2}}}{{{({{B}_{H}})}_{1}}}}\Rightarrow {{T}_{2}}={{T}_{1}}\sqrt{\frac{{{({{B}_{H}})}_{1}}}{{{({{B}_{H}})}_{2}}}}\] Here n1=30 oscillation /min \[=\frac{1}{2}\]oscillation/sec \[\therefore \ \frac{\mu }{4\pi }.\frac{{{m}^{2}}}{{{r}^{2}}}=50gm-wt\] \[\therefore {{T}_{2}}=2\sqrt{\frac{{{B}_{H}}}{2{{B}_{H}}}}=2\times \frac{1}{\sqrt{2}}=\sqrt{2}\sec \]


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