Question about Nodal Analysis Problem

Thread Starter

freemindbmx

Joined Mar 5, 2014
72
I need to determine Ix,could I transform the constant current source into a voltage source and then use nodal analysis?B/c if I didn't transform it and tried to label two nodes, it seems like I wouldn't be able to figure out the node voltage at the current source.Or just what your thoughts would be on determining this.
 

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Jony130

Joined Feb 17, 2009
5,488
You have two nodes. Treat upper node as a Vx and lower node as a GND.
And write KCL for the upper Vx node.
9A + (40 - Vx)/8 = Vx/4 + ??
 

Thread Starter

freemindbmx

Joined Mar 5, 2014
72
Im confused on the the node that has the 2 ohm resistor in parallel with the 9A current source. Going counter-clockwise at the Vx node when labeling the KCL. I1+Ix+I2=0.Current leaving the node(Vx) is positive.

I1= I have trouble labeling this one
Ix=Vx/4
I2=(Vx-40)/8

woud we just say its -9 A since its going in the opposite direction as my convention?
 

Jony130

Joined Feb 17, 2009
5,488
Im confused on the the node that has the 2 ohm resistor in parallel with the 9A current source. Going counter-clockwise at the Vx node when labeling the KCL. I1+Ix+I2=0.Current leaving the node(Vx) is positive.
Maybe this image can help you



Because in your KCL you simply forgot about 2 ohm resistor current.

I1= I have trouble labeling this one
Ix=Vx/4
I2=(Vx-40)/8
woud we just say its -9 A since its going in the opposite direction as my convention?
Yes, I1 = -9A
 

shteii01

Joined Feb 19, 2010
4,644
you mean place vx here and ground here?Im alittle confused as what you think is the upper part and lower part,could you expand on this?
9 A independent current source and 2 Ohm resistor and 4 Ohm resistor are all in parallel to each other. They all have same top node and bottom node. So. They all have Vx at the top and ground on the bottom. So the voltage drop across 2 Ohm resistor is Vx, the voltage drop across 4 Ohm resistor is also Vx.
 

Thread Starter

freemindbmx

Joined Mar 5, 2014
72
ahhh,shoulda seen they were in parallel and I havnt had a problem with multiple nodes(as depicted, I mean) such as the picture stated above,never knew this.Thanks
 
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