this is my first post

This is my first post.
What is the likely solution to the attached problem. Appreciate your assistance.

Favour,

One of the resistors connected to the dependent voltage source is missing a value. Ratch

Favor, please see: http://forum.allaboutcircuits.com/showthread.php?t=3002

Ratch
Thanks for your observation.
All.
Please find attached the updated attachment.
Will appreciate your assistance.

thingmaker3,
I opened two thread for two different circuit questions. Are you now saying that I should have merged the two attachment in one thread?

Sincerely, I do not know how to go about the two problems. Can someone help?

My apologies, the second file was similar enough to the first I thought it was the same one. Comparing them side by side, they are obviously different. I have re-opened the second thread.

Favour,

Looks to me like they want you to disconnect the east loop and Thevininize at the point of disconnection. Do you have a problem doing that? When you have a Thevinin impedance and voltage, connect up the east loop again and figure the voltage across Ro. Then check by doing a loop analysis to find the current of the east loop and the voltage across Ro. Can you do loop analysis? Ask for help if you have difficulty. Ratch

Ratch
Thanks for all your effort.
If I apply loop analysis (say mesh), how do I handle the dependent source (2vx), 2A current between two loops. It seems I will end up having four loops with four unknown. I am confused and do not know how to obtain a solution. Appreciate if you will assist.

When you are doing mesh analysis involving dependant sources, you do not know the voltage drop in the loop containing the dependant (voltage) source.

So the trick is to establish node current equations to include the current through the dependant source.

This will not yield enough equations to solve the mesh by itself.

So you then form voltage loop equations, from loops not involving the dependant voltage source.

You will then have enough equations to solve the mesh.

Have a go yourself at this before we do it for you.

I have tried solving it. Got Rth as 3 ohms (though not sure). Having problem with the appropriate and correct loop equation. Please help me!

Favour,

Sorry I did not catch it before, but you have to specify the polarity of VX. In other words, is the dependent voltage source sensing VX as if the negative lead of a voltmeter were on the north side or south side of resistor VX? Ratch

Sorry Ratch, partly my fault, there are no voltage sources in this circuit, only current sources.

Attached set of equations for the loop analysis. Best layout I could get in Word.

studiot,

Sorry Ratch, partly my fault, there are no voltage sources in this circuit, only current sources.

Click to expand...

Isn't that a dependent voltage source in the southwest loop dependent on the voltage across the 2 ohm resistor in the northeast loop? If so, we have to know how to connect the voltage sense leads across the 2 ohm resistor.

The problem states to first Thevinize the circuit, and then check it be analyzing the whole circuit using loop analysis.

Ratch

No Ratch it was me not reading the circuit thoroughly. The symbol with the arrow inside is a current source. The voltage dependency is a constant times some voltage elsewhere in the circuit. In this case twice the voltage across resistor CF.

The other two sources, shown by arrows in circles, are independent current sources.

You were correct in noting that a dependent voltage source has polarity markings, but it has no arrow.

Feel free to do the Thevenin analysis, I did the (bulk of) more onerous loop analysis.

I think one of the points of the exercise was to show how judicious use of Thevenin can shorten an analysis. The loop analysis involves solving 9 simultaneous equations.

studiot,

OK, you convinced me that it is indeed a dependent current source. But we still need polarity signs on on the 2 ohm resistor in order to know which way the voltage is being measured by the dependent current source. Ratch

I apologise I have to admit to a bobo the last equation in my loop analysis should read

Loop EFCHGE 2I7 -2I4 + I3 + 2I3 -4I6 = 0

The loop I too hastily chose contains one of the independent curent sources so, of course, the voltage across it can't be included.
I have uploaded a replacemnt page in this post.

Ratch, please check your textbook on circuit analysis.

I said in post 12 and I will say again.

There are no voltages sources, dependant or independent in this circuit.

All the voltages are entirely determined by the displayed circuit parameters; the polarity of the voltage VX across the 2 ohm resistor can be found in the analysis.

I superimposed my stuff on the original word document. I have just noticed that resistor DE was not labelled in the original so I have updated my loop analysis to include the value of 2 ohms from the subsequent pdf.

I have also added another equation to account for the unknown voltage VX.

So here is the latest version, please ignore (or mods remove) versions 1 and 2.

studiot,

I am still looking for some polarity marks by the resistor for VX. For instance, would the negative voltage sense lead from the dependent current source connect to the north or south side of the resistor? In other words, where are the polarity markings for the sense resistor? Ratch

studiot,

Ratch, please check your textbook on circuit analysis.

Click to expand...

Since this particular problem in not in any of the books on circuit analysis I have, they do not help me.

I said in post 12 and I will say again.

There are no voltages sources, dependant or independent in this circuit.

Click to expand...

True, but irrelevant. There is a voltage across resistor VX, and I have to know how it is measured before analysis can begin. Look at this voltage controlled current source and notice how the voltage leads are labeled. http://www.freeda.org/doc/elements/vccs.pdf That is the way the resistor VX should be marked. Ratch