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JEE Main & Advanced Physics Semiconducting Devices Question Bank Critical Thinking

  • question_answer
    The contribution in the total current flowing through a semiconductor due to electrons and holes are \[\frac{3}{4}\] and \[\frac{1}{4}\] respectively. If the drift velocity of electrons is \[\frac{5}{2}\] times that of holes at this temperature, then the ratio of concentration of electrons and holes is

    A)            6 : 5                                          

    B)            5 : 6

    C)            3 : 2                                          

    D)            2 : 3

    Correct Answer: A

    Solution :

                       As we know current density J = nqv Þ \[{{J}_{e}}={{n}_{e}}q{{v}_{e}}\] and \[{{J}_{h}}={{n}_{h}}q{{v}_{h}}\] Þ \[\frac{{{J}_{e}}}{{{J}_{h}}}=\frac{{{n}_{e}}}{{{n}_{h}}}\times \frac{{{v}_{e}}}{{{v}_{h}}}\] Þ \[\frac{3/4}{1/4}=\frac{{{n}_{e}}}{{{n}_{h}}}\times \frac{5}{20}\] Þ \[\frac{{{n}_{e}}}{{{n}_{h}}}=\frac{6}{5}\]


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