CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2007

  • question_answer
    A proton and a deuteron with the same initial kinetic energy enter a magnetic field in a direction perpendicular to the direction of the field. The ratio of the radii of the circular trajectories described by them is

    A)  \[1:4\]                                 

    B)  \[1:\sqrt{2}\]

    C)  \[1:1\]                                 

    D)  \[1:2\]

    Correct Answer: B

    Solution :

    For a moving charge in a perpendicular magnetic field,                 \[\frac{m{{v}^{2}}}{r}=Bqv\] \[\Rightarrow \]               \[r=\frac{mv}{Bq}=\frac{P}{Bq}\] or            \[\frac{{{r}_{p}}}{{{r}_{d}}}=\frac{{{P}_{p}}}{{{P}_{d}}}\]                                               ... (i)                                                 (as q is same for both) Also, momentum \[p=\sqrt{2\,mE}\] or            \[\frac{{{P}_{p}}}{{{P}_{d}}}=\sqrt{\frac{{{m}_{p}}}{{{m}_{d}}}}\]                                             ... (ii) From Eqs. (i) and (ii), we have,                 \[\frac{{{r}_{p}}}{{{r}_{d}}}=\sqrt{\frac{{{m}_{p}}}{{{m}_{d}}}}=\sqrt{\frac{1}{2}}=\frac{1}{\sqrt{2}}\]


You need to login to perform this action.
You will be redirected in 3 sec spinner