Please help; what this Question meaning

Discussion in 'Electrical Forum discussion & Blog' started by Amy 212, May 7, 2008.

  1. Amy 212

    Amy 212 New Member

    Messages:
    2
    I don’t understand how to solve this question -

    “Find the sinusoid magnitude and phase “in degrees†at 0.5 ms for this

    V(t)= 5 sin (2π * 500 t + π/4 ) [V]


    Thanks alot ...
    Amy212
  2. arfeller

    arfeller New Member

    Messages:
    77
    Location:
    Port Angeles, WA
    Is that symbol after the "2?" and "?/4" PI?
    And can we assume the units of t is seconds?
    Last edited: May 8, 2008
  3. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    This is a straight forward solution. You just don't have all the information.

    I don't specifically recognize or remember that equation from my electrical/electronic school days. But it would make sense if your "n" was pi. You have given t as 0.5 ms, so all you need to plug in a value for V and git'r'done.
  4. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    The formula as given is a little confusing, what with that [V] term dangling out there. If we assume t in seconds, and [V] just some arbitrary constant, you could express your answer in terms of [V]. All you really have to do is find the value of the sine function for t=.0005 seconds, which turns out to be .707. Thus the answer would be 3.535[V], but again I have no idea how to interpret the [V] term...

    For t=.0005, the argument of the sine function evaluates to 0.5pi + pi/4 = 3*pi/4. Since 2pi radians = 360 degrees, the phase is 135 degrees. This is consistent with the value of the sine function, 0.707, which is the value of a sine function at any multiple of 45 degrees.

    Was [V] originally written as |V|, by any chance? That would make sense.
    Last edited: May 8, 2008
  5. Amy 212

    Amy 212 New Member

    Messages:
    2
    Hi guys;

    I sorry;

    V(t)= 5 sin (2pi * 500 t + pi/4 ) [V]

    My problem i do not understand what "magnitude" mean?



    And thanks again.
    Last edited: May 8, 2008
  6. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

    Messages:
    2,716
    Location:
    Central Florida
    Magnitude would be the value of the function. For example, the magnitude (value) of a sine wave can be anything from -1 to +1. In my answer above, the magnitude of the function V(t) for t=.0005 was 3.535.
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