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Railways NTPC (Technical Ability) Instrument Mechanical Question Bank Instrument Mechanical

  • question_answer
    In the statement, "in a reaction turbine installation, the head of water is decreased and the rpm is also decreased at a certain condition of working. The effect of each of these changes will be to X power delivered due to decrease in head and to \[\gamma \] power delivered due to decrease in rpm?. \[\frac{N\sqrt{Q}}{{{H}^{3/4}}}\] X and Y stand respectively for:

    A) Decrease and increase

    B) Increase and increase

    C) Decrease and decrease

    D) Increase and decrease.

    Correct Answer: A

    Solution :

    For a reaction turbine, \[P\alpha {{H}^{3/2}}\]. Thus decrease of head would result in decrease of power developed. \[N\alpha \frac{1}{\sqrt{P}}\] Or \[P\alpha \frac{1}{{{N}^{2}}}.\] thus decrease in speed will result in increase in power.


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