WB JEE Medical WB JEE Medical Solved Paper-2015

  • question_answer
    Two particles, A and B, having equal charges, after being accelerated through the same potential difference enter into a region of uniform magnetic field and the particles describe circular paths of radii \[{{R}_{1}}\]and\[{{R}_{2}},\] respectively. The ratio of the masses of A and B is

    A)  \[\sqrt{{{R}_{1}}/{{R}_{2}}}\]

    B)  \[{{R}_{1}}/{{R}_{2}}\]

    C)  \[{{({{R}_{1}}/{{R}_{2}})}^{2}}\]

    D)  \[{{({{R}_{2}}/{{R}_{1}})}^{2}}\]

    Correct Answer: C

    Solution :

     Radius of circular path followed by charged particle is given by \[R=\frac{mv}{qB}=\frac{\sqrt{2mK}}{qB}\]   \[[\because \,p=mv=\sqrt{2mK}]\] where, \[K\]is kinetic energy of particle. Charged particle q is accelerated through some potential difference V, such that kinetic energy of particle is \[K=qV,\] \[\therefore \] \[R=\frac{\sqrt{2mqV}}{qB}\] As the two charged particles of same  magnitude and being accelerated through same potential, enters into a uniform magnetic field region, then \[R\propto \sqrt{m}\] So, \[\frac{{{R}_{1}}}{{{R}_{2}}}=\sqrt{\frac{{{m}_{A}}}{{{m}_{B}}}}\Rightarrow \frac{{{m}_{A}}}{{{m}_{B}}}={{\left( \frac{{{R}_{1}}}{{{R}_{2}}} \right)}^{2}}\]


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