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Passive and active elements?

  1. Oct 2, 2015 #1
    upload_2015-10-2_13-27-44.png

    p here stands to power (v in power equation is magnitude), in addition to this : is it also true that in the first one : V = RI (V upper - V lower) and in the second one : V = - RI (V lower - V upper) ?
    (current is magnitude in all previous equations)
     

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    Last edited: Oct 2, 2015
  2. jcsd
  3. Oct 2, 2015 #2

    berkeman

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    Staff: Mentor

    It's not clear what your question is, but on the quoted part, no. A resistor does not generate power. You can have a voltage source with an internal resistance value, but the voltage source is what is generating the power, and the internal resistance of the power source consumes some of that power as the load current flows through it.
     
  4. Oct 2, 2015 #3
    upload_2015-10-3_0-23-18.png

    so is this example wrong ? it treated v2 as -RI and v2 appeared to be negative at the end, which stated that resistance + and - ends are reversed i think
     
  5. Oct 2, 2015 #4

    berkeman

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    Staff: Mentor

    I think they are just trying to illustrate how if you choose the voltage drops incorrectly initially when using KVL, you still get the right answers in the end (because you get a negative number which means the voltage drop is actually in the other direction).
     
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