JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2010

  • question_answer     The ratio of electron and hole currents in a semiconductor is 7/4 and the ratio of drift velocities of electrons and holes is 5/4 then ratio of concentrations of electrons and holes will be

    A)  5/7                                       

    B)  7/5

    C)  25/49                                   

    D)  49/25

    Correct Answer: B

    Solution :

                    \[I=n\,A\,e\,{{v}_{d}}\]or\[I\propto n{{v}_{d}}\] \[\therefore \]  \[\frac{{{I}_{e}}}{{{I}_{h}}}=\frac{{{n}_{e}}{{V}_{e}}}{{{n}_{h}}{{v}_{h}}}\] Or           \[\frac{{{n}_{e}}}{{{n}_{h}}}=\frac{{{I}_{e}}}{{{I}_{h}}}=\frac{{{v}_{h}}}{{{v}_{e}}}\]                 \[=\frac{7}{4}\times \frac{4}{5}=\frac{7}{5}\]

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