NEET AIPMT SOLVED PAPER SCREENING 2012

  • question_answer
    An alternating electric field of frequency v, is applied across the dees (radius =R) of a cyclotron that is being used to accelerate protons (mass = m). The operating magnetic field (B) used in the cyclotron and the kinetic energy (1C) of the proton beam, produced by it, are given by

    A) \[B=\frac{mv}{e}\]and\[K=2m{{\pi }^{2}}{{v}^{2}}{{R}^{2}}\]

    B) \[B=\frac{2\pi mv}{e}\]and\[K={{m}^{2}}\pi v{{R}^{2}}\]

    C) \[B=\frac{2\pi mv}{e}\]and\[K=2m{{\pi }^{2}}{{v}^{2}}{{R}^{2}}\]

    D) \[B=\frac{mv}{e}\]and\[K={{m}^{2}}\pi v{{R}^{2}}\]

    Correct Answer: C

    Solution :

    Frequency \[v=\frac{eB}{2\pi m}\] \[KE=\frac{1}{2}m{{v}^{2}}\]and radius\[R=\frac{mv}{eB}\] Here, velocity \[v=\frac{\pi R}{T/2}=\frac{2\pi R}{T}=2\pi Rv\] \[\therefore \]Radius \[R=\frac{m(2\pi Rv)}{eB}\] Magnetic field \[B=\frac{2\pi mv}{e}\]Kinetic energy \[K=\frac{1}{2}m{{(2\pi Rv)}^{2}}=2m{{\pi }^{2}}{{v}^{2}}{{R}^{2}}\]


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