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Homework Help: Period of a Sine Function

  1. Jun 18, 2017 #1
    1. The problem statement, all variables and given/known data
    Given the wave form, determine the period, frequency, peak amplitude, peak to peak amplitude, voltage offset, phase angle, signal equation, rms voltage.

    2. Relevant equations

    3. The attempt at a solution

    Hi! So the main issue I'm having with this problem is reading the values I need from this graph. I uploaded a picture of the wave and a helpful diagram of a sine wave that define what all the values I need are.

    I know that the period is the distance between the peaks of the wave. I've seen some people divide the number of waves in the graph by the amount of time on the x axis of the graph. So for this case T=7/(50x10-6 = 7.143, which by eye-balling it it seems to be close.

    For the peak amplitude, I think it is 0.5.

    The peak to peak amplitude, I think it is 0.6

    The voltage offset, I don't know how to find. Is there some sort of formula I'm missing?

    I don't know how to find the phase angle.

    The signal equation and rms voltage should be easy to find after I have all the other values.

    Thank you for any help.

    Attached Files:

  2. jcsd
  3. Jun 19, 2017 #2


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    See the waveform carefully. What are the peak and valley points on the waveform?
  4. Jun 19, 2017 #3
    The first step is to write down the general form of the equation you are trying to fit to the data. This is missing from your Relevant Equations.
  5. Jun 20, 2017 #4


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    Actually, using the terminology of the OP's second attachment, that was correct; the peak amplitude is 0.5 V. "Peak amplitude" here is not to be confused with "signal amplitude."

    @jdawg, don't forget your units.

    [Edit: Be careful what you are doing here. Are you calculating the period or the frequency? They are inverses of each other. So once you find one it's easy to find the other. Just make sure you don't confuse the two.]
    As mentioned above, I agree.
    That looks right to me. Again though, don't forget your units.
    It is possible to quantify this with a formula, but for this exercise you can eyeball it.
    It is possible to quantify this with a formula, but again, for this exercise you can eyeball it. [Edit: it will be somewhere between 0 and 360o if you represent it in degrees, or it will be between 0 and [itex] 2 \pi [/itex] if you represent it in units of radians. Either way, you should be able to eyeball it for this exercise.]
    The rms voltage of a sine wave either requires prior knowledge about rms voltage of sine waves, or you can derive it yourself with calculus. You'll also need to know how the voltage offset fits into the overall rms voltage (or find it yourself with calculus). The easiest way is to look up these relationships in your coursework.
    Last edited: Jun 20, 2017
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