Circuit Analysis with nodal analysis

Discussion in 'Homework Help' started by Hooperoo, Apr 5, 2013.

  1. Hooperoo

    Thread Starter New Member

    Apr 5, 2013
    1
    0
    Hi guys.
    Im tearing my hair out over this problem, so any help would be greatly appreciated.

    [​IMG]

    Im solving the circuit with nodal analysis, and following the steps of:
    1: Ground node equation
    2: Voltage source and current source equations
    3: Equations for each resistor
    4: KCL at each node apart from the ground node
    5: Substituting resistor equations into the KCL equations and solving for the node voltages
    6: Solve for branch currents
    7: Find power consumed or supplied

    The problem is, i get to step 5, find a node voltage, but apparently it's the wrong answer. It doesn't match any of the answers supplied by the teacher (it's a practice multiple choice exam).

    Attached is my working, with a picture of the circuit.

    I get to a voltage for node B (circled in red), however, when I sub this in to find the voltage at node A, i get the wrong answer (12.8).

    Please please please tell me what I am doing wrong.

    Thank you in advance
     
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    You already know that

    \frac{V_A-V_B}{3000}=I_1=I_4=5mA

    So VA is of no consequence in the solution.

    You then only have to find VB given VC is also known.
     
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