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NEET Sample Paper NEET Sample Test Paper-11

  • question_answer
    A coil of inductive reactance\[31\,\Omega \]has a resistance of\[8\,\Omega .\]It is placed in series with a condenser of capacitive reactance\[25\,\Omega \]. The combination is connected to an AC source of 110 V. The power factor of the circuit is

    A)  0.56

    B)  0.64

    C)  0.80

    D)  0.33

    Correct Answer: C

    Solution :

     Power factor\[(cos\phi )\]is a ratio of resistance and impedance of AC circuit. Power factor of AC circuit is given by \[\cos \phi =\frac{R}{Z}\]                                                (i) Where R is resistance employed and Z the imped- ance of the circuit. \[Z=\sqrt{{{R}^{2}}+({{X}_{L}}-X_{C}^{2})}\]                                (ii) Eqs. (i) and (ii) meet to give, \[\cos \phi =\frac{R}{\sqrt{{{R}^{2}}+{{({{X}_{L}}-{{X}_{C}})}^{2}}}}\] Given, \[R=8\Omega ,{{X}_{L}}=21\Omega ,{{X}_{C}}=25\Omega \] \[\cos \phi =\frac{8}{\sqrt{{{(8)}^{2}}+{{(31-25)}^{2}}}}=\frac{8}{\sqrt{64+36}}\] \[\cos \phi =0.80\]


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