# Having trouble with superposition.....

Discussion in 'Homework Help' started by nirvanaguy, Oct 4, 2009.

1. ### nirvanaguy Thread Starter New Member

Oct 3, 2009
15
0
At least that's what I think this problem involves

So..
a) determine the contribution to Vx from each source in the circuit.. b) what is the total value of Vo? c) if the values of Ia and Ib are interchanged, what value of Vo results?

I tried doing nodal analysis at each point but got a totally wrong answer like Vx=-.588 V...

I don't really know what i'm doing in this question.. i would REALLY appreciate any help or tips on how to approach solving this problem

2. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
One approach would be to convert each current source and its shunt (parallel) resistor to a Thevenin equivalent. This might make the analysis a little easier. You could still apply superposition - by treating each source individually and adding the two results algebraically.

See how you go.

Try to post some of your working - it makes our task at lot easier in terms of knowing where to help.

3. ### nirvanaguy Thread Starter New Member

Oct 3, 2009
15
0
ok well what i did was I looked at each nodes on the top left , middle, and top right
, naming them V1, Vx, and V2, respectively

for superposiitioning the 3A source by itself, I got
-3 + (V1 - 0)/12 + (V1 - Vx)/6 = 0
(Vx - V1)/6 + (Vx - 0)/9 + (Vx - V2)/6 = 0
(V2 - Vx)/6 + (V2 - 0)/12 = 0

For superpositioning the 2 a osurce by itself, i got:
(V1 - 0)/12 + (V1 - Vx)/6 = 0
(Vx - V1)/6 + (Vx - 0)/9 + (Vx - V2)/6 = 0
(V2 - Vx)/6 + (V2 - 0)/12 - 2 = 0

I'm not SURE if the second equation is right, though, because nodal analysis is taken for all the current that goes AWAY from the node.. but someone told me that all 3 terms should be positive.. when I think it should be first and 3rd term being negative and the middle one being positive.. wrong or right??

Doing it out his way I got the answer to be 6 V for the superpostiion of the 2 A source
and i got 9V for the superposition of the 3 A source..

Last edited: Oct 4, 2009