RAJASTHAN ­ PET Rajasthan PET Solved Paper-2005

  • question_answer
    The ratio of gravitational and electric forces between two electrons.

    A)  \[{{10}^{-36}}\]            

    B)  \[{{10}^{-39}}\]

    C)  \[{{10}^{-42}}\]            

    D)  \[{{10}^{-47}}\]

    Correct Answer: C

    Solution :

     The gravitational force between two electrons \[{{F}_{G}}=\frac{G{{m}^{2}}}{{{r}^{2}}}\] and electric force \[{{F}_{E}}=\frac{1}{4\pi {{\varepsilon }_{0}}}.\frac{{{e}^{2}}}{{{r}^{2}}}\] \[\therefore \] \[\frac{{{F}_{E}}}{{{F}_{G}}}=\frac{\frac{1}{4\pi {{\varepsilon }_{0}}}.\frac{{{e}^{2}}}{{{r}^{2}}}}{G{{m}^{2}}}\] \[=\frac{9\times {{10}^{9}}\times {{(1.6\times {{10}^{-19}})}^{2}}}{6.67\times {{10}^{-11}}\times {{(9.1\times {{10}^{-31}})}^{2}}}\] \[\approx {{10}^{42}}\] Or \[\frac{{{F}_{E}}}{{{F}_{G}}}={{10}^{-42}}\]


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