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!

Nodal and Mesh mismatch..where am I going wrong

  1. Feb 8, 2016 #1
    upload_2016-2-8_15-48-6.png

    Given the circuit diagram above, I am interested in finding the current ia. Using mesh analysis, I determined it to be 1.71mA, but nodal analysis results in a value of 2.25mA. Solution attempts provided below. I think the issue is in my nodal analysis approach.

    Mesh Analysis..I1 is the left mesh, I2 the right mesh.
    upload_2016-2-8_15-52-53.png

    Nodal analysis attempt...current calculation at the bottom.
    upload_2016-2-8_15-53-45.png
     

    Attached Files:

  2. jcsd
  3. Feb 8, 2016 #2

    gneill

    User Avatar

    Staff: Mentor

    For the node equation, check your substitution for v1: Note that the 6 V source is connected through a resistor to the reference potential.
     
  4. Feb 8, 2016 #3
    I tried to take that into account on one of my attempts, the voltage v1 as 3-v provides the correct value for current. I was unsure if I'm on solid ground to do that.

    upload_2016-2-8_16-13-31.png
     
  5. Feb 8, 2016 #4

    gneill

    User Avatar

    Staff: Mentor

    You're on the right track. But how to justify your substitution?

    Consider that you have a term in your node equation for the current that passes through the "v1" resistor. How would you express v1 in terms of that current?
     
  6. Feb 8, 2016 #5
    I see v1 given as

    upload_2016-2-8_16-33-6.png
    Which allows me to plug in and

    upload_2016-2-8_16-33-45.png
     
  7. Feb 8, 2016 #6

    gneill

    User Avatar

    Staff: Mentor

    Looks good.
     
  8. Feb 8, 2016 #7
    Thank you.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted