KVPY Sample Paper KVPY Stream-SX Model Paper-30

  • question_answer
    For a LCR series circuit with an A.C. source of angular frequency \[\omega .\]

    A) Circuit will be capacitive if \[\omega >\frac{1}{\sqrt{LC}}\]

    B) Circuit will be inductive if \[\omega =\frac{1}{\sqrt{LC}}\]

    C) Power factor of circuit will be unity if capacitive reactance equals inductive reactance

    D) Current will be leading voltage if \[\omega >\frac{1}{\sqrt{LC}}\]

    Correct Answer: C

    Solution :

    The circuit will have inductive nature if \[\omega >\frac{1}{\sqrt{LC}}\left( \omega L>\frac{1}{\sqrt{LC}} \right)\]
    Hence A is false. Also if circuit has inductive nature the current will lag behind voltage. Hence D also false
    If \[\omega >\frac{1}{\sqrt{LC}}\left( \omega L=\frac{1}{\omega C} \right)\] the circuit will have resistance nature. Hence B is false
    Power factor \[\cos \phi =\frac{R}{\sqrt{{{R}^{2}}+{{\left( \omega L-\frac{1}{\omega C} \right)}^{2}}}}=1\]
    If \[\omega L=\frac{1}{\omega C}.\]
    Hence C is true


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