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NEET Sample Paper NEET Sample Test Paper-54

  • question_answer
    A beam of cathode rays accelerated across potential difference V is subjected to crossed Electric (E) and Magnetic fields [B]. The fields are adjusted such that the beam is not deflected. The specific charge of the cathode rays is given by-

    A) \[\frac{{{E}^{2}}}{2V{{B}^{2}}}\]               

    B) \[\frac{{{B}^{2}}}{2V{{B}^{2}}}\]

    C) \[\frac{2V{{B}^{2}}}{{{E}^{2}}}\]               

    D)  \[\frac{2V{{E}^{2}}}{{{B}^{2}}}\]

    Correct Answer: A

    Solution :

    \[qvB\,\,=\,\,qE\,\,\,\Rightarrow \,\,v=\,\,\frac{E}{B}\] But \[\frac{1}{2}m{{v}^{2}}=qV\] \[\frac{q}{m}=\frac{{{v}^{2}}}{2V}=\frac{{{E}^{2}}}{2V{{B}^{2}}}\]


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