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NEET Sample Paper NEET Sample Test Paper-51

  • question_answer
    Pure silicon at 300 K has equal electron ne and hole \[({{n}_{h}})\] concentration of \[1.5\,\,\times \,\,{{10}^{16}}\,{{m}^{-}}^{3}\]. Doping by indium increases \[{{n}_{h}}\] to \[4.5\,\,\times \,\,{{10}^{22}}\,{{m}^{-}}^{3}\]. The \[{{n}_{e}}\] in the doped silicon is (in per \[{{m}^{3}}\])-

    A) \[9\,\,\times \,\,{{10}^{5}}\]                 

    B) \[5\times {{10}^{9}}\]

    C) \[2.25\times {{10}^{11}}\]                   

    D) \[3\times {{10}^{19}}\]

    Correct Answer: B

    Solution :

    \[{{n}_{i}}=1.5\times {{10}^{16}}\] \[{{n}_{h}}=4.5\times {{10}^{22}}\] \[Law\,\,of\text{ }mass\text{ }action\text{ }{{n}_{e}}{{n}_{h}}=n_{i}^{2}\] \[{{n}_{e}}=\,\,\frac{n_{i}^{2}}{{{n}_{h}}}\,\,=\,\,\frac{{{(1.5\times {{10}^{16}})}^{2}}}{(4.5\times {{10}^{22}})}\] \[{{n}_{e}}\,\,=\,\,5\times {{10}^{9}}\,\left( \frac{1}{{{m}^{3}}} \right)\]


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