Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Maximum Amplitude, 50hx vs 60hz generator

  1. Jan 30, 2008 #1
    1. The problem statement, all variables and given/known data

    We have an AC generator with output current I. I, as a function of time, is a sine wave whose frequency, f, is the same as the rotational frequency of the generator. So,

    I(t) = I[tex]_{0}[/tex]sin(2πft), where I[tex]_{0}[/tex] is the max. amplitude of the current.

    In terms of magnetic flux, [tex]\Phi[/tex][tex]_{B}[/tex]:

    I = - (Constant * Change in [tex]\Phi[/tex][tex]_{B}[/tex]) / time

    When the generator revolves at 50 revs/second, the maximum amplitude I[tex]_{0}[/tex] = 1000 A. If you increase the spead of the generator to 60 revs/sec, what is the maximum amplitude I[tex]_{0}[/tex]?

    2. Relevant equations

    Given above


    3. The attempt at a solution

    This question really stumped me. It's difficult to bring in additional equations since we don't know more about the generator -- it's obviously a concept question. I suspect that the maximum amplitude will increase proportionally.

    We know that f(old) = 50 Hz, since it will be the same as the rotatation frequency. Thus, the period for this sine curve will be 1/50 second, as the amplitude goes from maximum to maximum. When f(new) = 60 Hz, the period will condense to 1/60 second.

    Thinking about flux, there is no change in magnetic field (B) -- though the [tex]\Theta[/tex] between B and the area of the coil will be changing faster as rotations speed up. So change in fluz would be greater over a given unit of time (???). Thus, from the second equation, we know that I must also increase (???).

    At this point, I simply guess that the change will be proportional -- since rotation is increasing in speed by 20%, so will maximum amplitude ??????????????


    Thanks for your help!
     
    Last edited: Jan 30, 2008
  2. jcsd
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Similar Discussions: Maximum Amplitude, 50hx vs 60hz generator
  1. Maximum Total Yield? (Replies: 0)

  2. Amplitude Question (Replies: 0)

  3. Pressure Amplitude (Replies: 0)

Loading...