Homework: Determind if the dependent source absorbs or supplied power to the circuit

Thread Starter

michgkou

Joined Oct 3, 2019
37
Hi all,

I wonder if I'm on the right track. Because, using LTspice the results are Va=-12, Vb=7.13 and Vc=27.47 volts.

Thanks.

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Jony130

Joined Feb 17, 2009
5,127
You know what, none of your two solutions is correct. Why? Because you made the same error in your hand calculation and in LTspice. In simply words your "definition" of an I3 (and Vx voltage) current is wrong.

How can I3 be equal to I3 = (Vc - 9V) /1Ω?

Do you see the error?
 
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Thread Starter

michgkou

Joined Oct 3, 2019
37
You know what, none of your two solutions is correct. Why? Because you made the same error in your hand calculation and in LTspice. In simply words your "definition" of an I3 (and Vx voltage) current is wrong.

How can I3 be equal to I3 = (Vc - 9V) /1Ω?

Do you see the error?
So the I3=(Vc+9-Vb)/1 ?
 

Thread Starter

michgkou

Joined Oct 3, 2019
37
I'm comfused here. At the right side is Vc and at tthe lift side Vb, and what about 9V. this is incorrect I3=(Vc+9-Vb)/1 (?)Καταγραφή.PNG
 

Thread Starter

michgkou

Joined Oct 3, 2019
37
Do you know that the voltage between points C and B is (Vc - Vb)?
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Yes, now I understand. I draw again the circuit making source transformation and help me.

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You might be interested in seeing how it can be done in very compact form using linear algebra techniques.

The network is solved using both nodal and mesh analysis.

For the nodal analysis, I included the non-essential node between the 9 volt source and the 1 ohm resistor.

For the mesh analysis, the meshes and currents are I1, the lower left mesh; I2, the lower right mesh; I3, the upper mesh.

From these two solutions, the current in the dependent source is I3, and the voltage across the dependent source is Vd-Va.

NodalMesh.png
 
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