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Do i add these in paralell?

  1. Oct 27, 2005 #1
    Hello everyone i have the follwoing circuit:
    http://www.webassign.net/hrw/hrw7_27-34.gif I need to find the Potential Difference between a and b. I found the current of R1 and R2, and the questions says:
    R1 = 130 , R2 = 75 , and the ideal batteries have emfs E1 = 6.0 V, E2 = 5.5 V, E3 = 4.0 V.

    R1 current = .042A
    R2 current = .0467

    Im confused on what I should add u using kricofs rule? like do i just say
    Va = -E2 -E3+ R1*i2 + Vb
    Va -Vb = -E2 -E3+ R1*i2
    But there is a resistor that looks like paraellel, but is that R1 parellel to R2?
     
  2. jcsd
  3. Oct 27, 2005 #2

    Tom Mattson

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    Not to me they don't!

    Certainly not. To be in parallel they have to have the same potential difference across them no matter what the values of [itex]\mathcal{E}_1[/itex], [itex]\mathcal{E}_2[/itex], and [itex]\mathcal{E}_1[/itex] which is clearly not the case.

    Also, note that [itex]R_1[/itex] is in parallel with [itex]\mathcal{E}_2[/itex], but that [itex]R_2[/itex] is not in parallel with [itex]\mathcal{E}_2[/itex]. Since they are not both in parallel with [itex]\mathcal{E}_2[/itex], there is no way that they could possibly be in parallel with each other.
     
  4. Oct 27, 2005 #3

    Tom Mattson

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    That's not right. If you follow the path from [itex]a[/itex] to [itex]b[/itex] you do not go through [itex]R_1[/itex].
     
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