10th Class Science Electricity and Circuits Question Bank Electricity

  • question_answer
    If two electrons are separated by a distance of \[0.\text{5}\overset{\circ }{\mathop{\text{A}}}\,\], then ratio of coulomb force and weight of electron is approximately

    A) \[\text{1}{{0}^{\text{16}}}\]                     

    B)         \[\text{1}{{0}^{\text{18}}}\]

    C) \[\text{1}{{0}^{\text{2}0}}\]                      

    D)         \[\text{1}{{0}^{\text{22}}}\]  

    Correct Answer: D

    Solution :

                    \[F=\frac{1}{4\pi {{\varepsilon }_{0}}}\cdot \frac{{{q}_{1}}{{q}_{2}}}{{{r}^{2}}}\]                     \[=9\times {{10}^{9}}\times \frac{{{q}_{1}}{{q}_{2}}}{{{r}^{2}}}\]                     \[=9\times {{10}^{9}}\frac{(1.6\times {{10}^{-19}})(1.6\times {{10}^{-19}})}{{{(0.5\times {{10}^{-10}})}^{2}}}\]                     \[=\mathbf{9}\mathbf{.2\times 1}{{\mathbf{0}}^{\mathbf{-8}}}\mathbf{N}\] Weight,\[W=mg\]                    \[=(9.1\times {{10}^{-31}})(9.8)\]                    \[=8.9\times {{10}^{-30}}N\] \[\therefore \]       \[\frac{F}{W}=\frac{9.2\times {{10}^{-8}}}{8.9\times {{10}^{-30}}}\approx {{10}^{22}}\]


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