Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Find the node voltages of the circuit

  1. Sep 11, 2011 #1
    1. The problem statement, all variables and given/known data

    [PLAIN]http://img339.imageshack.us/img339/6089/electriccircuits221revi.png [Broken]

    2. Relevant equations

    i = v/R

    3. The attempt at a solution

    My attempt at the solution is all in the red in the diagram above. Apparently the book's answers are 1 V and 2 V and it doesn't say which voltage corresponds with what but I'll assume v1 = 1 V and v2 = 2 V. When I solved for v2 with my equation I got 20 V. Can someone help me out with getting the equations set up so I can solve for the voltages? I drew the loops I used in red. Since there's 2 unknowns, I need at least 2 equations. Problem is, I don't know if my equations are correct.
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Sep 11, 2011 #2


    User Avatar
    Homework Helper

    You calculate the algebraic sum of currents at the nodes V1 and V2. There is no sense to draw the loops, note the currents in each branch connected to the nodes V1 and V2 instead.

  4. Sep 11, 2011 #3
    Yeah someone pointed out to me I have to do node analysis. I ended up getting the book's answer for part a. How would I find the net resistance for part b? The hint is kind of confusing me.
  5. Sep 11, 2011 #4
    Anyone got any sort of hint for part b? It doesn't look like i can use the formula's for resistors in series and parallel here the way the circuit is set up but I may be over thinking it.
    Last edited: Sep 11, 2011
  6. Sep 11, 2011 #5


    User Avatar
    Homework Helper

    The net resistance seen by the source is equal to the generator voltage divided by the generator current. Write the sum of currents at the node connected to the ground, and find the current flowing into the generator.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook