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AMU Medical AMU Solved Paper-2008

  • question_answer
    An electric motor runs on DC source of emf 200 V and draws a current of 10 A. If the efficiency be 40% then the resistance of armature is

    A)  2 a                                        

    B)  8 a

    C)  12 i2                                     

    D)  16 a

    Correct Answer: C

    Solution :

                     Input power\[=VI=200\times 10\]                                 = 2000 W Output power \[=\frac{40}{100}\times 200=800\,W\] Power loss in heating the armature                                 = 2000 - 800                                 = 1200 W \[\therefore \]  \[{{I}^{2}}R=1200\] or            \[R=\frac{1200}{{{I}^{2}}}\]                 \[=\frac{1200}{10\times 10}\] or            R = 12 \[\Omega \]


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