Rate of change of voltage over time?

Discussion in 'General Electronics Chat' started by vead, Aug 17, 2016.

  1. vead

    Thread Starter Active Member

    Nov 24, 2011
    621
    8
    Hello
    I am not sure the examples, that I am taking is correct. I have taken values just for my understanding. Example:Capacitor is connected to 20 V battery. Voltage of capacitor increase or decrease at the particular movement of time. I want to find out voltage across capacitor at any moment of time
    _20160817_133122.JPG
    From the graph, it can be seen that voltage before 5 second will less than 20 V and voltage after 5 seconds will less than 20 V.
    _20160817_133122.JPG _20160817_134508.JPG
    How to find out voltage at specific time?
     
  2. Marley

    Member

    Apr 4, 2016
    144
    40
    Of course it depends on the resistance of the 20V source.
    See this. Not sure why your graph goes back to zero?

    If the source has a reactive impedance it gets a lot more complicated!

    I'm sure there are mathematical geniuses out there who can give you a formula for that!
     
  3. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,546
    1,252
    Your charts are not correct for a capacitor connected to a battery. A battery will charge the capacitor up to the battery voltage. The capacitor voltage will then sit there until the capacitor is disconnected from the battery.

    There are two common equations for determining how a capacitor's voltage changes with time. One is based on the capacitor being connected to a constant voltage source through an impedance. The other is based on the capacitor being connected to a constant current source.

    ak
     
  4. MrSoftware

    Active Member

    Oct 29, 2013
    504
    124
    Strictly from a math point of view (assuming you have data and don't care that it came from electrical components), then this thread covers creating an equation to fit the line pretty nicely:

    http://math.stackexchange.com/questions/121212/how-to-find-curve-equation-from-data

    When you have real data, and you figure the equation for the curve, then you should be able to plug a time into the equation and come out with an approximate voltage for that time.
     
    Last edited: Aug 17, 2016
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