MGIMS WARDHA MGIMS WARDHA Solved Paper-2007

  • question_answer
    If emf E = 4 cos 1000t volt is applied to an L-R circuit of inductance 3 mH and resistance 40\[\Omega \] the amplitude of current in the circuit is

    A)  \[\frac{4}{\sqrt{7}}A\]                                 

    B) \[1.0A\]

    C) \[\frac{4}{7}A\]                                

    D) \[0.8A\]

    Correct Answer: D

    Solution :

    \[Z=\sqrt{{{R}^{2}}+X_{L}^{2}}\] Here, \[R=4\Omega ,{{X}_{L}}=L\omega =3\times {{10}^{-3}}\times 1000\Omega \]                                 \[=3\Omega \] Then,          \[Z=\sqrt{{{(4)}^{2}}+{{(3)}^{2}}}\]                 \[Z=\sqrt{16+9}=\sqrt{25}\]                 \[Z=5\,\Omega \] Hence, current \[{{I}_{0}}=\frac{{{E}_{0}}}{z}=\frac{4}{5}=0.8\,A\]


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