J & K CET Engineering J and K - CET Engineering Solved Paper-2013

  • question_answer
    If     the     alternating     current \[I={{I}_{1}}\,\,\cos \,\,\,\omega t+{{I}_{2}}\,\,\sin \,\,\omega t\](of  then  the  rms current is given by

    A)  \[\frac{{{I}_{1}}+{{I}_{2}}}{\sqrt{2}}\]

    B)  \[\frac{|{{I}_{1}}+{{I}_{2}}|}{\sqrt{2}}\]

    C)  \[\sqrt{\left( \frac{I_{1}^{2}+I_{2}^{2}}{2} \right)}\]

    D)  \[\sqrt{\frac{I_{1}^{2}+I_{2}^{2}}{\sqrt{2}}}\]

    Correct Answer: C

    Solution :

    The equation of AC is \[I={{I}_{1}}\cos \,\omega t+{{I}_{2}}\,\,\sin \,\omega L\] The resultant current is given by \[{{I}_{0}}=\sqrt{I_{1}^{2}+I_{2}^{2}}\] Hence, the rms current from relation is \[{{I}_{rms}}=\frac{{{I}_{0}}}{\sqrt{2}}=\frac{\sqrt{I_{1}^{2}+I_{2}^{2}}}{\sqrt{2}}\] \[=\sqrt{\frac{I_{1}^{2}+I_{2}^{2}}{2}}\]


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