1. Not finding help here? Sign up for a free 30min 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!

Potential difference between two points (VA - VB)

  1. Jun 4, 2016 #1
    1. The problem statement, all variables and given/known data
    Q. With the switch closed, what is the voltage difference, VA-VB ?

    Untitled.png

    2. Relevant equations
    Junction rule: I3 = I1 + I2
    Loop rule(s)

    3. The attempt at a solution
    I solved for the currents in this circuit when the switch is closed.

    Top loop(clockwise): +10V1 - 15*I1 - 47*I1 + (0V since i'm assuming no Voltage drop across switch) = 0
    Bottom loop(counter clockwise): -5*I2 + 6V2 - 22*I2 + 0V = 0

    For the top loop: I isolated I1 and got 10/62 = 0.161 = I1
    For the bottom loop: I got 6/27 = 0.222A = I2
    I1 + I2 = 0.161 + 0.222 = 0.383A.= I3

    for the voltage difference VA - VB, I tried doing this with the guidance of a friend.
    Va = 10 - I1*15 = 7.585 V.
    Vb = Va - Vc - 6 (Vc being the voltage at node C where I3 flows through.)
    Then Vc = Va - i1*47 = 7.585 - (7.567) = 0.018 V.
    Vb = Va - Vc - 6 = 7.585 - 0.018 - 6 = 1.567 V.
    Finally Va - Vb = 7.585 - 1.567 = 6.018 V

    I am not sure whether I did this part correct.
     
  2. jcsd
  3. Jun 4, 2016 #2

    NascentOxygen

    User Avatar

    Staff: Mentor

    You already have a thread dealing with this circuit. You must keep all related questions in that thread.

    This thread will be deleted shortly.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook