A) \[21/6\]
B) \[5\]
C) \[3/8\]
D) \[2\]
Correct Answer: D
Solution :
When some potential difference is applied across a piece of intrinsic semiconductor current flows in it due to both electron and holes ie, \[I={{I}_{e}}+{{I}_{h}}\] Moreover,\[{{I}_{e}}=eA{{n}_{e}}{{v}_{e}}\] ...(i) If, \[{{I}_{h}}=eA{{n}_{h}}{{v}_{h}}\] ...(ii) Now, dividing Eqs. (i) and (ii), we get \[\frac{{{I}_{e}}}{{{I}_{h}}}=\frac{{{n}_{e}}}{{{n}_{h}}}\frac{{{v}_{e}}}{{{v}_{h}}}\] or \[\frac{(4/5)I}{(1/5)I}=\frac{{{n}_{e}}}{{{n}_{h}}}\times \frac{2{{v}_{h}}}{{{v}_{h}}}\] \[\left[ \begin{align} & Given\,\,\,{{v}_{e}}=2{{v}_{h}} \\ & {{I}_{e}}=\frac{4}{5}I \\ & and\,\,{{I}_{h}}=\frac{1}{5}I \\ \end{align} \right]\] \[\Rightarrow \] \[\frac{{{n}_{e}}}{{{n}_{h}}}=2\]
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