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Total voltage, current and resistance

  1. May 18, 2008 #1
    I'm having problems understanding the voltage and current in resistors.

    Basically, when resistors are placed in parrallel or series, how are you meant to work out the current and voltage running in each?

    I was under the assumption you find the total current running in the circuit (when given V and the total resistance of the resistors in series or parralel, usually being you have to calculate the total resistance cause they're usually in parrallel).
    Then you use this current to calculate the voltage running through it.

    Or is it the other way round? I'm clueless on this!

    Any help would be oh so perfect!
  2. jcsd
  3. May 18, 2008 #2
    Yes. First calculate the total (resulting) resistance of all resistors together. You can (usually) do this when the resistors are in parrallel, series or a combination of both (do you know how?).

    Assuming you know the voltage of the source, you can then calculate the total current through the circuit using ohm's law, V = IR.

    An important 'detail' now is that the current through resistors in series will be equal, while the current over resistors in parrallel will not. (The current splits up between the two paths).

    Once you know the current you can then use ohm's law again for each resistor R seperately to find the voltage over that resistor.
  4. May 18, 2008 #3


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    Just apply Ohm and Kirchoff's Laws or use a volt-ohm-ammeter and measure them.

    I recommend going through examples in your textbook on these types of problems (applications of Ohm's Law). Start with the easy ones and work your way to more challenging ones. As you practice these, the answer to your question will become clear.
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