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Voltage vs. Time Graph

  1. Oct 20, 2009 #1
    What are you able to derive or integrate from a voltage vs. time graph? Like if I have a battery and a resistor and want to know the charge after so many hours or seconds.
    We went over this in class but could someone elaborate the relationship?
     
  2. jcsd
  3. Oct 20, 2009 #2
    A battery across a resistor, voltage is constant, graph of voltage versus time is a horizontal straight line. Are you sure that your real question isn't about a capacitor?
     
  4. Oct 20, 2009 #3
    I had a problem the teacher gave us and it was a graph of time(x-axis) vs. voltage(y-axis) and it had the line as a negative slope where the voltage of the battery was 1.5V and it crossed the y-axis at 3 hours. they gave us a resistor of x ohms.
    So there is no capacitor in the problem and how should I treat it?

    *note this is not a homework question, just a general one
     
  5. Oct 21, 2009 #4
    You're question is a bit confusing... I'll try to help...
    I'll assume:
    -You're saying the battery's voltage is reducing linearly from 1.5V to 0V over a three hour duration.
    -You're circuit is a battery with a resistor across it.
    -You said something about charge, so I'll assume current.

    Current, I=V/R

    If you integrate that function, you get 0.5*(1.5V)/R*time. For example, let's assume that R=10 Ohms:
    Then you could calculate: 0.5*1.5/10*3hr = 225mAh (milli amp hours).

    But this is actually a useless calculation. Can you elaborate on your question?
     
  6. Oct 21, 2009 #5
    I think the person needs:
    decreasing 1.5 volts in 10800 seconds, for a slope of -0.0001389 volts per second
    V = (-0.0001389 V/s) t + 1.5 V
     
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