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Uttarakhand PMT Uttarakhand PMT 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)  20             

    B)  80

    C)  120          

    D)  160

    Correct Answer: C

    Solution :

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


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