JEE Main & Advanced Physics Magnetic Effects of Current / करंट का चुंबकीय प्रभाव JEE PYQ-Magnetic Effects Of Current

  • question_answer
    A proton and a deuteron are both accelerated through the same potential difference and enter in a magnetic field perpendicular to the direction of the field. If the deuteron follows a path of radius R, assuming the neutron and proton masses are nearly equal, the radius of the proton's path will be                                       [JEE ONLINE 19-05-2012]

    A) \[\sqrt{2}R\]

    B)  \[\frac{R}{\sqrt{2}}\]

    C) \[\frac{R}{2}\]

    D) R

    Correct Answer: B

    Solution :

    [b] As charge on both proton and deuteron is same i.e. 'e'
    Energy acquired by both, E = eV
    For Deuteron.
    Kinetic energy, \[=\frac{1}{2}m{{V}^{2}}=eV\]
    [V is the potential difference]\[v=\sqrt{\frac{2eV}{{{m}_{d}}}}\]
    But\[{{m}_{d}}=2m\]
    Therefore, \[v=\sqrt{\frac{2eV}{2m}}=\sqrt{\frac{eV}{m}}\]
    Radius of path, \[R=\frac{mv}{eB}\]
    Substituting value of V we get\[R=\frac{2m\sqrt{\frac{ev}{m}}}{eB}\]
    \[\frac{R}{2}=\frac{m\sqrt{\frac{ev}{m}}}{eB}\]                                                …(i)
    For proton:
    \[\frac{1}{2}m{{V}^{2}}=eV\]
    \[V=\sqrt{\frac{2eV}{m}}\]
    Radius of path, \[R'=\frac{mV}{eB}=\frac{m\sqrt{\frac{2eV}{m}}}{eB}\]
    \[R'=\sqrt{2}\times \frac{R}{2}\][From eq. (i)]\[R'=\frac{R}{2}\]


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