Manipal Engineering Manipal Engineering Solved Paper-2013

  • question_answer
    The correct relation between\[\alpha \]and\[\beta \]in a transistor is

    A) \[\beta =\frac{\alpha }{1-\alpha }\]                        

    B) \[\beta =\frac{\alpha }{1+\alpha }\]

    C) \[\beta =\frac{1+\alpha }{\alpha }\]       

    D)        \[\beta =1-\alpha \]

    Correct Answer: B

    Solution :

    We know that                 \[\alpha =\left( \frac{\Delta {{i}_{C}}}{\Delta {{i}_{E}}} \right)\]                                  ... (i) and        \[\beta =\left( \frac{\Delta {{i}_{C}}}{\Delta {{i}_{E}}} \right)=\frac{\Delta {{i}_{C}}}{\Delta {{i}_{E}}}\times \frac{\Delta {{i}_{E}}}{\Delta {{i}_{B}}}\]                     \[=\alpha \frac{\Delta {{i}_{E}}}{\Delta {{i}_{B}}}\]                                        ... (ii) But\[\Delta {{i}_{B}}=\Delta {{i}_{E}}-\Delta {{i}_{C}}\] from (ii)          \[\beta =\alpha \frac{\Delta {{i}_{E}}}{\Delta {{i}_{E}}-\Delta {{i}_{C}}}=\frac{\alpha }{1-\frac{\Delta {{i}_{C}}}{\Delta {{i}_{E}}}}\] \[\therefore \]     \[\beta =\frac{\alpha }{1-\alpha }\]


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