NEET Physics Alternating Current / प्रत्यावर्ती धारा NEET PYQ-Alternating Current

  • question_answer
    A resistance 'R' draws power 'P' when connected to an AC source. If an inductance such that the impedance of the circuit becomes 'Z' the power drawn will the                                                                                   [NEET  2015]

    A)  \[P{{\left( \frac{R}{Z} \right)}^{2}}\]               

    B)  \[P\sqrt{\frac{R}{Z}}\]  

    C)  \[P\left( \frac{R}{Z} \right)\]       

    D)       P

    Correct Answer: A

    Solution :

    When a resistor is connected to an AC source. The power drawn will be
                \[p={{V}_{rms}}/{{I}_{rms}}={{V}_{rms}}.\frac{{{V}_{rms}}}{R}\]
    \[\Rightarrow \]   \[V_{rms}^{2}=PR\]
    When an inductor is connected in series with the resistor, then the power drawn will be
                            \[P'={{V}_{rms}}.{{I}_{rms}}\cos \phi \]
    where, \[\phi \]= phase difference
    \[\therefore \]   \[P'=\frac{V_{rms}^{2}}{R}.\frac{{{R}^{2}}}{{{Z}^{2}}}=p.R.\frac{R}{{{Z}^{2}}}\]
    \[\Rightarrow \,\,\,\,\,p'=\frac{p.{{R}^{2}}}{{{Z}^{2}}}=P{{\left( \frac{R}{Z} \right)}^{2}}\]


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