12th Class Physics Alternating Current / प्रत्यावर्ती धारा Question Bank MCQ - Alternating Currents

  • question_answer
    The voltage over a cycle varies as \[V={{V}_{0}}\sin \omega t\] for \[0\le t\le \frac{\pi }{\omega }\] \[=-{{V}_{0}}\sin \omega t\] for \[\frac{\pi }{\omega }\le t\le \frac{2\pi }{\omega }\] The average value of the voltage for one cycle is:

    A) \[\frac{{{V}_{0}}}{\sqrt{2}}\]                          

    B) \[\frac{{{V}_{0}}}{2}\]

    C) zero                              

    D) \[\frac{2{{V}_{0}}}{\pi }\]

    Correct Answer: D

    Solution :

    (d) \[\frac{2{{V}_{0}}}{\pi }\] The average value of the voltage is \[{{V}_{av}}=\frac{\int{_{0}^{2\pi /\omega }\,V\,dt}}{\int{_{0}^{2\pi /\omega }dt}}\] \[=\frac{\int{_{0}^{\pi /\omega }{{V}_{0}}\sin \omega t\,\,dt+\int{_{\pi /\omega }^{2\pi /\omega }(-{{V}_{0}}sin\omega t)dt}}}{\frac{2\pi }{\omega }}\] \[=\frac{\omega }{2\pi }\left[ \left| \frac{-{{V}_{0}}\cos \,\omega t}{\omega } \right|_{0}^{\pi /\omega }+\left| \frac{{{V}_{0}}\cos \,\omega t}{\omega } \right|_{\pi /\omega }^{2\pi /\omega } \right]=\frac{2{{V}_{0}}}{\pi }\]


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