And here is where I get to preach about units!!!

First, it's only partly your fault because the original problem was sloppy with the units (in a way-too-common manner).

I commented on this in the other thread here:

https://forum.allaboutcircuits.com/...ode-voltage-method.144908/page-2#post-1230213

The dependent source is a current controlled voltage source, so the output of the source is 9 V for every 1 A of input current through the sensor. Hence the gain is 9 V/A or 9 Ω.

What YOU should have done is murmured all kinds of bad things at the author while you were verifying that they had all the units correct and then, after seeing that they didn't, putting the missing "V/A" or "Ω" on the "9".

That way, when you properly tracked your units, your first equation would have been

I2 = I4 + I3

which would have then become

I2 = 9Ω·I + I3

and you would have immediately said, "Huh! What! Something's WRONG!" and then discovered almost immediately that you are working with a voltage source, not a current source.

I'll continue to harp on this -- tracking units properly pays off!!!

 

Ok @WBahn ... I didn't know that the 9 were ohms. I thought it was just a factor of gain, therefore, dimensionless!

I'll try to look to the circuit again today during work if I can find a few minutes.

Thanks
Psy