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Homework Help: Calculating Vrms

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  1. Nov 22, 2016 #1
    1. The problem statement, all variables and given/known data

    9jozS67.png

    imgur link: https://i.imgur.com/9jozS67.png

    2. Relevant equations

    3. The attempt at a solution

    Shouldn't I use [itex]V_{rms} = \sqrt{\frac{1}{T}\int_T v^2 dt}[/itex]?

    Which would be

    [tex]\sqrt{\frac{100}{2\pi}\int_0^{2\pi/100}(20+60cos(100t))^2dt}[/tex]

    This equals [itex]\approx 79.88 V[/itex]

    The answer is given as [itex]\approx 46.9V[/itex] and the solution manual shows the following working

    [tex]\sqrt{20^2 + \frac{60^2}{2}}[/tex]

    Why do they apply that solution and not the one I used?
     
  2. jcsd
  3. Nov 22, 2016 #2

    gneill

    User Avatar

    Staff: Mentor

    You might want to check your integration. I find that the integral matches the manual's result.
     
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