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Electrical Engineering - Energy Graph Question

  1. Sep 13, 2010 #1
    1. The problem statement, all variables and given/known data
    Question number 3!, I attached it. Need help!

    Figure 1 shows the current through and the voltage across a device. Find the total energy absorbed by the device fore the period 0<t<4.


    2. Relevant equations
    integral of p = energy
    P=VI


    3. The attempt at a solution
    Just need the algorithm to solving these kinds of problems, I am kind of thrown off at the instantaneous change.
     

    Attached Files:

  2. jcsd
  3. Sep 13, 2010 #2
    One way you could think about this problem is by taking discrete intervals on the current graph and voltage graph and multiplying these values together. This will result in a graph that describes the power dissipation in the device over the given time interval. Then it will just be a matter of finding the area under the curve (integrating the resulting power function).
     
  4. Sep 14, 2010 #3
    Yeah I thought about that approach but when I look at the voltage it comepletely throws me off. I am able to break the current into 2 seperate intervals with the function y1=25x and 0<t<2, y2=-25x 2<t<4, but for the voltage at t=2 its constant and I cant come up with a function to multply with my current.
     
  5. Sep 14, 2010 #4
    For the voltage between t=1 and t=3, the function describing the voltage is just a constant, or y=10.
     
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