JEE Main & Advanced Physics Alternating Current / प्रत्यावर्ती धारा Question Bank Self Evaluation Test - Alternating Current

  • question_answer
    An arc lamp requires a direct current of 10 A at 80 V to function. If it is connected to a 220 V (rms),50 Hz AC supply, the series inductor needed for it to work is close to :

    A) 0.044 H            

    B) 0.065 H

    C) 80 H             

    D)        0.08 H

    Correct Answer: B

    Solution :

    [b] Here \[i\,=\frac{e}{\sqrt{{{R}^{2}}+X_{L}^{2}}}=\frac{e}{\sqrt{{{R}^{2}}+{{\omega }^{2}}{{L}^{2}}}}=\frac{e}{\sqrt{{{R}^{2}}+4{{\pi }^{2}}{{v}^{2}}\,{{L}^{2}}}}\] \[10\,=\frac{220}{\sqrt{64+4{{\pi }^{2}}\,{{(50)}^{2}}\,L}}\] \[\left[ \because \,\,R=\frac{V}{I}=\frac{80}{10}=8 \right]\] On solving we get L = 0.065 H


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