AIIMS AIIMS Solved Paper-2009

  • question_answer
    In the Bohrs model of a hydrogen atom, the centripetal force is furnished by the Coulomb attraction between the proton and the electron. If \[{{a}_{0}}\] is the radius of the ground state orbit, m is the mass, e is the charge on electron and \[{{\varepsilon }_{0}}\] is the permittivity of free space, the speed of the electron is

    A) \[\frac{e}{\sqrt{{{\varepsilon }_{0}}{{a}_{0}}m}}\]           

    B)                       zero                      

    C)       \[\frac{e}{\sqrt{4\pi {{\varepsilon }_{0}}{{a}_{0}}m}}\]

    D)       \[\frac{\sqrt{4\pi {{\varepsilon }_{0}}{{a}_{0}}m}}{e}\]

    Correct Answer: C

    Solution :

                    Coulomb attraction between electron and proton \[=\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{{{e}^{2}}}{{{r}^{2}}}\] Centripetal force \[=\frac{m{{v}^{2}}}{r}\] \[\therefore \]   \[\frac{m{{v}^{2}}}{r}=\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{{{e}^{2}}}{{{r}^{2}}}\] \[\Rightarrow \]   \[{{v}^{2}}=\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{{{e}^{2}}}{mr}\] For ground state of H-atom \[r={{a}_{0}}\] \[\therefore \,\,\,\,\,\,\,\,\,\,\,\,v=\frac{e}{\sqrt{4\pi {{\varepsilon }_{0}}m{{a}_{0}}}}\]


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