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Constant voltage sources! Help please

  1. Sep 23, 2007 #1
    Hey guys

    I am new to Electrical Eng, i got a question to answer, it says that a variable resistor is connected to a " Constant Voltage Source", how does the current through the resistor changes as its resistance varies from zero to infinity?

    I also need with the same question, but with a ideal constant Voltage source and real constant vol source!

  2. jcsd
  3. Sep 23, 2007 #2


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    Do you know Ohms Law? If so, see how the current is related to voltage and resistance. Remember, the voltage is constant.
  4. Sep 23, 2007 #3
    Yeh V = R*I, Since for the first V = Constant, Then I = V/R, I = 1/r, but what is the difference between ideal, real, and voltage constant sources!,

  5. Sep 23, 2007 #4


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    There are many subtle differences, and one big one. What happens to the current draw from an ideal source as the load resistance goes to zero? Would you expect the same behavior from a real source?
  6. Sep 23, 2007 #5
    Can u give me some definitions for ideal and real sources and how the ohm's law works with those! And how resistance affects the current in those sources.

    thanks and sorry really new with circuits and all!
  7. Sep 23, 2007 #6


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    Real voltage sources have an internal resistance - draw it as a battery with a small resistor in series. Now image you have a 12V battery with an internalal resistance of 1Ohm, as you draw 1Amp from the battery there is a 1V drop accross the internal resistor and so you only get 11V out. What's the maximum current you can draw from such a battery?
    AN ideal source has a zero Ohm internal resistance.
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