J & K CET Engineering J and K - CET Engineering Solved Paper-2005

  • question_answer
    If an electron moves from rest from a point at which potential is \[50\text{ }V\]to another point at which potential is \[70\text{ }V,\] then its kinetic energy in the final state will be

    A)  \[3.2\times {{10}^{-20}}J~\]

    B)  \[3.2\times {{10}^{-18}}J\]

    C) \[3.2\times {{10}^{-19}}J\]  

    D)  zero

    Correct Answer: B

    Solution :

    The kinetic energy acquired by the particle is \[KE=q\Delta V\] where q is charge and \[\Delta V\] the change in potential difference. Given,   \[q=e=1.6\times {{10}^{-19}}C\] \[\Delta V={{V}_{2}}-{{V}_{1}}=70-50=20V\] \[\therefore \] \[KE=1.6\times {{10}^{-19}}\times 20=3.2\times {{10}^{-18}}J\]


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