BCECE Engineering BCECE Engineering Solved Paper-2010

  • question_answer
    An AC source is 120 V-60 Hz. The value of voltage after\[\frac{1}{720}\] from start will be

    A)  20.2 V                                  

    B)  42.4 V

    C)  84.8 V                  

    D)         106.8 V

    Correct Answer: C

    Solution :

    From \[V={{V}_{0}}\sin \omega t\] \[V={{V}_{rms}}\sqrt{2}\sin \omega t\]                 After     \[t=\frac{1}{720}s,\]                                 \[V=120\sqrt{2}\sin 2\pi v\,t\]                                 \[=120\sqrt{2}\sin 2\pi \times 60\times \frac{1}{720}\]                                 \[=120\sqrt{2}\sin \frac{\pi }{6}\] \[=120\sqrt{2}\times \frac{1}{2}\] \[=60\sqrt{2}=84.8\,V\]


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