BHU PMT BHU PMT Solved Paper-2002

  • question_answer
    The current gain \[4\times {{10}^{8}}\,m/s\] of a transistor is 0.95. The Change in emitter current\[2.25\times {{10}^{8}}\,m/s\]. The radium lift After 4800 years.                                       [BHU PMT-2002]

    A)                  \[3\times {{10}^{8}}\,m/s\]                       

    B)                  \[1600\,\,A{{m}^{-1}}\]

    C)                  \[2.4\times {{10}^{-5}}\,\,Wb\]                               

    D)                  \[0.2\,c{{m}^{2}}\]

    Correct Answer: C

    Solution :

                     Key Idea: Emitter current is sum of base current and collector current.                 Current gain is defined as the ratio of the change in collector current \[\frac{256\,R}{81}\]                 \[\frac{81\,R}{256}\]                       \[\frac{16\,R}{9}\]                 Also, \[\frac{9\,R}{16}\]= \[n\]+ \[\frac{3}{2}n\], where \[\frac{n}{2}\] is base current.                 \[2n\]   \[n\]                          \[{{T}_{1}}\]                 \[{{T}_{2}}\left( {{T}_{1}}>{{T}_{2}} \right).\]\[{{C}_{p}}\left( {{T}_{1}}-{{T}_{2}} \right)\]                                 \[{{C}_{V}}\left( {{T}_{1}}-{{T}_{2}} \right)\]                 \[R\left( {{T}_{1}}-{{T}_{2}} \right)\]        \[Zero\]                 Note: The base being very thin, the number of hole-electron combinations in it is very small and almost all the holes entering the base from the emitter reach the collector. Hence, \[x\] is slightly less than\[x\].


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