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!

Should Vout be negative or positive?

  1. Jan 26, 2013 #1
    I attached the circuit.

    I did kirkoff's voltage law (assuming current goes clockwise):
    -15+5-10,000I-40000I=0 where I=current
    I=-2*10^-4 A

    V_out=40,000*-2*10^-4A = -8V
    The way V_out is shown, it should solve to be negative, correct?
     

    Attached Files:

  2. jcsd
  3. Jan 26, 2013 #2

    gneill

    User Avatar

    Staff: Mentor

    Correct.
     
  4. Jan 26, 2013 #3

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    V is the difference betwen potentials at two places in the circuit.
    If you look at the voltage sources, the top is less positive than the bottom - so the bottom must have a higher potential than the top. Replace the voltage sources with an equivalent single voltage source and the answer to your question will become clear.

    Note: when you do kirkoffs laws to analyze a circuit - draw voltage arrows on the components as well as current arrows at the nodes.
     
  5. Jan 26, 2013 #4
    Did you solve the problem?
    I'm asking because if you didn't, can you tell just by looking it that it will be negative?
     
  6. Jan 26, 2013 #5

    gneill

    User Avatar

    Staff: Mentor

    Yes, I can tell just by looking; But I've looked at a LOT of circuit problems over the years!

    I took note of the two voltage supplies and determined that the top of them will be negative w.r.t. the bottom. I then looked at the polarity specified for "measuring" the output and drew the conclusion that Vout must be negative.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Should Vout be negative or positive?
  1. Negative or Positive (Replies: 1)

Loading...