CET Karnataka Medical CET - Karnataka Medical Solved Paper-2002

  • question_answer
    Two copper balls, each weighing 10 g are kept in air 10cm apart. If one electron from every 10  atoms is transferred from one ball to the other, the coulomb force between them is: (atomic weight of copper is 63-5)

    A) \[2.0\times {{10}^{4}}N\]

    B)  \[2.0\times {{10}^{10}}N\]

    C)  \[2.0\text{ }{{10}^{6}}N\]

    D)  \[2.0\times {{10}^{8}}N\]

    Correct Answer: D

    Solution :

     No. of atoms in 10 gm of copper \[=\frac{6\times {{10}^{23}}\times 10}{63.5}=9.4\times {{10}^{22}}\]No- of \[\overline{e}\] transferred from one piece to other \[=\frac{9.4\times {{10}^{22}}}{{{10}^{6}}}=9.4\times {{10}^{16}}\]Charge on these electron \[\overline{e}=9.4\times {{10}^{16}}\times 1.6\times {{10}^{-19}}\] \[=15\times {{10}^{-3}}C\]equal but opposite charge will be on other piece \[\therefore \]\[\text{Fattraction}=\frac{{{q}_{1}}{{q}_{2}}}{4\pi {{\varepsilon }_{0}}{{r}^{2}}}\] \[=\frac{{{(1.5\times {{10}^{-2}})}^{2}}\times 9\times {{10}^{9}}}{0.01}\]\[=2\times {{10}^{7}}N\]


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