Calculating Equivalent Voltage in a Complex Circuit: Thevenin vs. Norton

[jisbon]

Homework Statement

Use source transformation to reduce the circuit to a single voltage source Vs in series with a single resistor R. What are the values of Vs and R?

Relevant Equations

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From this, I can transform the current source to:

I can then find the equivalent resistance to be (30//20)//40 = 9.23 ohms.
However, I am not sure how to find the equivalent voltage in this case?
What should I do to start?

 

[archaic]

That's a wrong transformation. Read this https://people.clarkson.edu/~jsvoboda/eta/dcWorkout/sourceXfrm.pdf a bunch of examples.

 

[jisbon]

That's a wrong transformation. Read this https://people.clarkson.edu/~jsvoboda/eta/dcWorkout/sourceXfrm.pdf a bunch of examples.

I don't seem to get it, isn't the transformation correct for the left side though?

 

[archaic]

I don't seem to get it, isn't the transformation correct for the left side though?

You have an extra wire that is making a short circuit.
And, by the way, wouldn't you think that transforming the voltage sources instead would be a better strategy?

 

[jisbon]

View attachment 267867
You have an extra wire that is making a short circuit.
And, by the way, wouldn't you think that transforming the voltage sources instead would be a better strategy?

Ah ok I get what you mean, so something like:

How do I exactly find the 'total' voltage in this case tho?

 

[willem2]

Ah ok I get what you mean, so something like:

View attachment 267868
How do I exactly find the 'total' voltage in this case tho?

You use the source transform to make the problem easier. non-ideal voltage sources in parallel are hard. Maybe you could transform the sources into something else?

 

[archaic]

Ah ok I get what you mean, so something like:

View attachment 267868
How do I exactly find the 'total' voltage in this case tho?

That is correct, but follow my advice, don't do that transformation.

 

[cnh1995]

I can then find the equivalent resistance to be (30//20)//40 = 9.23 ohms.

How do you know between which two points the equivalent resistance is asked? Ditto for "single voltage Vs".

I am not sure if I understood this problem correctly.

 

[jbriggs444]

How do you know between which two points the equivalent resistance is asked? Ditto for "single voltage Vs".

I am not sure if I understood this problem correctly.

The drawing does not make it explicit, but the fact that all of the top endpoints of the devices in the middle merge onto a single wire and that all of the bottom endpoints of the devices in the middle merge onto a single wire strongly suggests that those two wires are the two points between which equivalent resistance is desired.

[I had the same reaction at first]

 

[rude man]

You would be better served to change the two thevenin sections to norton sections so the whole thing is a bunch of Nortons in parallel.