1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Finding a voltage across 2 nodes [Check answer - work already done]

  1. Sep 26, 2011 #1
    1. The problem statement, all variables and given/known data

    blFU9.png

    2. Relevant equations



    3. The attempt at a solution
    I got V1=18V
    Here's my work:
    AdrND.jpg
     
  2. jcsd
  3. Sep 26, 2011 #2

    Zryn

    User Avatar
    Gold Member

    Can you repost the original question and then rewrite your solution with some brief explanations to show what you are doing? i.e KVL (Right): V1 - Vx - 24 = 0
     
  4. Sep 28, 2011 #3

    rude man

    User Avatar
    Homework Helper
    Gold Member

    I got V1 = 37.33V, Vx= 13.33V. It checks when you plug the numbers into your schematic.

    If V1 = 18V then Vx = 18 - 24 = -6V so i thru the 25K = -6/25 = 0.24 mA
    whereas i thru the 5K would then be
    (-3*6 - 18)/5 = -7.2 mA so that can't be right.
     
  5. Sep 28, 2011 #4

    Zryn

    User Avatar
    Gold Member

    Vab = Va - Vb. Assuming Va is at V1+ and Vb is at V1-, what is V1?

    Given V1, and using KVL around the right hand loop, what is Vx?
     
  6. Sep 28, 2011 #5

    rude man

    User Avatar
    Homework Helper
    Gold Member

    There are 2 loops? If so, V1 = 0!!
     
  7. Sep 29, 2011 #6

    Zryn

    User Avatar
    Gold Member

    Given the line drawn between V1+ and V1-, and the node 'dots', it seems a safe assumption that there are two loops, rather than just one with an errant line.

    I did it your way as well though and got the same numbers, but wanted the original question reposted just to verify.
     
  8. Sep 29, 2011 #7

    rude man

    User Avatar
    Homework Helper
    Gold Member

    Two loops were my firat assumption too, but then I realized that that would make the problem pathological (viz. V1 = 0). Also, the OP calculated a finite (albeit erroneous) V1. So I decided that extra line must indicate voltage rise gnd to V1, although I did wonder why there was no arrow at the top of that line. Also, if two loops, why did the OP have - and + signs next to that line?
     
  9. Sep 29, 2011 #8

    Zryn

    User Avatar
    Gold Member

    It could possibly have been designed as a (trick) knowledge problem, rather than a circuit analysis problem. Needs more OP confirmation I suppose.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Finding a voltage across 2 nodes [Check answer - work already done]
Loading...