12th Class Physics Electric Charges and Fields Question Bank MCQ - Electric Charges and Fields

  • question_answer
    The ratio of magnitude of electrostatic force and gravitational force for an electron and a proton is:

    A) \[6.6\times {{10}^{39}}\]

    B) \[2.4\times {{10}^{39}}\]

    C) \[6.6\times {{10}^{29}}\]

    D) \[2.4\times {{10}^{29}}\]

    Correct Answer: B

    Solution :

    (b) \[2.4\times {{10}^{39}}\] For an electron and a proton: Electrostatic force, \[\left| {{F}_{e}} \right|=\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{{{e}^{2}}}{{{r}^{2}}}\] Gravitational force, \[\left| {{F}_{g}} \right|=\frac{G{{m}_{e}}\,{{m}_{p}}}{{{r}^{2}}}\] \[\therefore \,\,\,\,\,\,\frac{\left| {{F}_{e}} \right|}{\left| {{F}_{g}} \right|}=\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{{{e}^{2}}}{G{{m}_{e}}{{m}_{p}}}\] \[=\frac{9\times {{10}^{9}}\times {{\left( 1.6\times {{10}^{-19}} \right)}^{2}}}{6.67\times {{10}^{-11}}\times 9\times {{10}^{-31}}\times 1.66\times {{10}^{-27}}}\] \[=2.4\times {{10}^{39}}\]


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