JIPMER Jipmer Medical Solved Paper-2007

  • question_answer
    An electron moves in a circular orbit with a uniform speed\[v\]. It produces a magnetic field B at the centre of the circle. The radius of the circle is proportional to

    A) \[\frac{B}{v}\]

    B)                                        \[\frac{v}{B}\]                  

    C) \[\sqrt{\frac{v}{B}}\]                     

    D)        \[\sqrt{\frac{B}{v}}\]

    Correct Answer: C

    Solution :

    The time period of electron moving in a circular orbit \[T=\frac{\text{circumference of circular path}}{\text{speed}}\]                     \[=\frac{2\pi r}{v}\] and equivalent current due to electron flow \[I=\frac{e}{T}=\frac{e}{(2\pi r\text{/}v)}=\frac{ev}{2\pi r}\] Magnetic field at centre of circle \[B=\frac{{{\mu }_{0}}I}{2r}=\frac{{{\mu }_{0}}ev}{4\pi {{r}^{2}}}\] \[\Rightarrow \]                               \[r\propto \sqrt{\frac{v}{B}}\]


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