# Homework Help: Super-node question, one equation or two?

1. Sep 8, 2014

### orangeincup

1. The problem statement, all variables and given/known data
Use the mesh current method to solve for the power dissipated

2. Relevant equations
v1+v2+..vn=0
i=v/R
p=i*v

3. The attempt at a solution
I was trying to solve the question using two equations,
eq1) 20=4*i1+i1
eq2) -90=9*i2+6*i2
eq3)i2-i1=6A...

So I obviously made a mistake since the 6A is doing nothing in my equations, and both equations 1 and 2 have no unknowns. Am I suppose to just use one equation, and use the super node as my second? How can I tell when I need to use only one equation?

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2. Sep 8, 2014

### donpacino

In both eq1 and eq2 you are missing the voltage drop Vo

3. Sep 8, 2014

### Staff: Mentor

You are asked to use mesh equations, so rather than a supernode, you want a supermesh. You should write one equation for the supermesh and one constraint equation tying the two "normal" mesh currents to the 6 A source.