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BCECE Engineering BCECE Engineering Solved Paper-2011

  • question_answer
    An electron at rest is accelerated through a potential difference of 200 V. If the electron acquires a velocity \[8.4\,\times {{10}^{6}}\,m/s,\] the value of e/m of electron is

    A)  \[1.76\,\times {{10}^{-4}}C/kg\]

    B)  \[1.76\,\times {{10}^{14}}C/kg\]

    C)  \[1.76\,\times {{10}^{11}}C/kg\]

    D)  \[1.76\,\times {{10}^{-16}}C/kg\]

    Correct Answer: C

    Solution :

    \[\frac{1}{2}m{{v}^{2}}=eV\]or \[\frac{e}{m}=\frac{{{v}^{2}}}{2V}=\frac{{{(8.4\times {{10}^{6}})}^{2}}}{2\times 200}\] \[=1.76\times {{10}^{11}}\,C/kg\]


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