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

  • Thread starter jisbon
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In summary: I had the same reaction at first]In summary, the two wires in the middle of the drawing are the points between which the equivalent resistance is desired.
  • #1
jisbon
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30
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
-
1597632087664.png

From this, I can transform the current source to:
1597632154939.png


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?
 
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  • #2
That's a wrong transformation. Read this https://people.clarkson.edu/~jsvoboda/eta/dcWorkout/sourceXfrm.pdf a bunch of examples.
 
  • #3
archaic said:
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?
 
  • #4
jisbon said:
I don't seem to get it, isn't the transformation correct for the left side though?
1505994858.png

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?
 
  • #5
archaic said:
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:

1597653428920.png

How do I exactly find the 'total' voltage in this case tho?
 
  • #6
jisbon said:
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?
 
  • #7
jisbon said:
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.
 
  • #8
jisbon said:
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.
 
  • #9
cnh1995 said:
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]
 
  • #10
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.
 

1. What is voltage?

Voltage is a measure of the potential difference between two points in an electrical circuit. It is often referred to as the "pressure" or "force" that drives electric current.

2. How is voltage measured?

Voltage is measured using a device called a voltmeter, which is connected in parallel to the circuit. The unit of measurement for voltage is volts (V).

3. What is the difference between voltage and current?

Voltage is the potential difference between two points, while current is the flow of electric charge. Voltage can be thought of as the "push" that causes current to flow.

4. What is the total voltage in a series circuit?

In a series circuit, the total voltage is equal to the sum of the individual voltages across each component. This means that as the current flows through each component, the voltage drops across each one.

5. How does voltage affect the brightness of a light bulb?

The brightness of a light bulb is directly related to the voltage applied to it. As the voltage increases, the current flowing through the bulb also increases, resulting in a brighter light. However, if the voltage is too high, it can cause the bulb to burn out.

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