Supertheorem in electronic circuit

Thread Starter

SUGHYA

Joined Aug 7, 2022
3
Hello, I was tasked with this problem with Vs = 13V
1659845432728.png

Using superposition to eliminate current source, I got I1 = 0.084A. Then I went ahead to find I1 again eliminating the voltage source, I see that r4 series with r3 parallel with r2 parallel with r1. Am I right? I got Multisim but the answer is different from mine do you have a tip? Thank you
 

crutschow

Joined Mar 14, 2008
30,420
Am I right?
Appears to be no.
Multisim is likely right.

The theorem says:
When you remove a source, it is replaced by its internal impedance.

So what are the internal impedances of an ideal current source and an ideal voltage source?

I don't think you used those values.
 
Last edited:

WBahn

Joined Mar 31, 2012
26,841
You really need to show your work in order to get effective help.

Also, just saying that I1 = 0.084 A isn't enough because there is not indication of what direction that current is flowing in. That is particularly important when using superposition.

Draw the modified circuits with the sources turned off. Remember that "turned off" means with their output set to zero. For a current source, that means that the circuit is modified so that zero current flows between the two terminals connected to the source. For a voltage source, that means that the circuit is modified so that zero voltage appears across the two terminal connected to the source.

Also, think carefully about what it means for two things to be in either series or parallel. To be in series, it means that whatever current flows in one component must flow in the other, while to be in parallel means that whatever voltage appears across one must appear across the other.
 

Thread Starter

SUGHYA

Joined Aug 7, 2022
3
Appears to be no.
Multisim is likely right.

The theorem says:
When you remove a source, it is replaced by its internal impedance.

So what are the internal impedances of an ideal current source and an ideal voltage source?

I don't think you used those values.
The internal resistance of ideal sources are 0. In this case the voltage source is shorted so in reality it should be 2 amps or less. However, i have only seen problems that short circuit wires make 0 current through resistors connected with it, in this case r2 and r4. Do you have any websites or videos I can use?
 

Thread Starter

SUGHYA

Joined Aug 7, 2022
3
Hello, I was tasked with this problem with Vs = 13V
View attachment 273327

Using superposition to eliminate current source, I got I1 = 0.084A. Then I went ahead to find I1 again eliminating the voltage source, I see that r4 series with r3 parallel with r2 parallel with r1. Am I right? I got Multisim but the answer is different from mine do you have a tip? Thank you
 

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WBahn

Joined Mar 31, 2012
26,841
The internal resistance of ideal sources are 0. In this case the voltage source is shorted so in reality it should be 2 amps or less. However, i have only seen problems that short circuit wires make 0 current through resistors connected with it, in this case r2 and r4. Do you have any websites or videos I can use?
Remember, to turn a source off you set its output to zero. If you set a current source to zero amperes, that means that no current can flow through it no matter how much voltage appears across it. This does not describe a short circuit, which results in no voltage across it no matter how much current flows through it. What does it describe?
 

WBahn

Joined Mar 31, 2012
26,841
You still are ignoring the direction that current is flowing in R1. You need to clearly define that, otherwise you are highly likely to end up subtracting the two results when you should add or vice versa.
 
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