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JEE Main & Advanced Physics Semiconducting Devices Question Bank Critical Thinking

  • question_answer
    A potential difference of 2V is applied between the opposite faces of a Ge crystal plate of area 1 cm2 and thickness 0.5 mm. If the concentration of electrons in Ge is 2 ´ 1019/m3 and mobilities of electrons and holes are \[0.36\frac{{{m}^{2}}}{volt-\sec }\] and \[0.14\frac{{{m}^{2}}}{volt-\sec }\] respectively, then the current flowing through the plate will be

    A)            0.25 A                                      

    B)            0.45 A

    C)            0.56 A 

    D)            0.64 A

    Correct Answer: D

    Solution :

                       \[\sigma =ne({{\mu }_{e}}+{{\mu }_{h}})=2\times {{10}^{19}}\times 1.6\times {{10}^{-19}}(0.36+0.14)\] \[=1.6\,{{(\Omega \text{-}m)}^{-1}}\] \[R=\rho \frac{l}{A}=\frac{l}{\sigma A}=\frac{0.5\times {{10}^{-3}}}{1.6\times {{10}^{-4}}}=\frac{25}{8}\Omega \] \ \[i=\frac{V}{R}=\frac{2}{25/8}=\frac{16}{25}A=0.64\,A\]


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