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!

Homework Help: Node Voltages Problem

  1. Oct 30, 2014 #1
    1. The problem statement, all variables and given/known data
    We are told to analyse the circuit in the diagram (ignore the texts) with the method of node voltages.

    Here is the answer:


    2. Relevant equations
    Kirchhoff's Current Law
    Kirchhoff's Voltage Law

    3. The attempt at a solution
    So far, all I have been able to get is the equation described by the top line of the matrix relation. However, there is no 0 by the resistance!

    Worse, the bottom equation looks to me like (1-alpha)*v_2. And I have no idea where v_2 is even defined, or how this is a valid KCL equation without the value or R_2 anywhere....

    Thank you in advance for any help!
  2. jcsd
  3. Oct 30, 2014 #2


    User Avatar

    Staff: Mentor

    Your diagram has labelled the nodes 1 and 2. So it is reasonable to assume that v1 corresponds to node 1's voltage and that v2 corresponds to node 2's voltage.

    It could be that when you are trying to recover the individual node voltage expressions that you are not correctly carrying out the matrix times vector operation?

    I do see one typo in the text's solution though. The resistor in the matrix's first term should be R1, not R.

    Why don't you try writing out the nodal analysis equations from scratch. They can always be be wedged into matrix form afterwards.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted