Parallel voltage sources circuit

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Homework Help Overview

The discussion revolves around a circuit involving parallel voltage sources and the calculation of currents through resistors R1, R2, and R3. Participants are exploring the setup and equations related to the circuit analysis.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to establish equations for the circuit and seeks validation of their correctness. Some participants question the assumptions made in the equations, particularly regarding current direction and the need for reference points in voltage calculations.

Discussion Status

Participants are actively engaging with each other's reasoning, providing feedback on the equations and discussing the implications of voltage drops and reference points. There is a mix of agreement and further questioning, indicating a collaborative exploration of the topic.

Contextual Notes

There are ongoing discussions about the necessity of defining a reference voltage and the implications of grounding in circuit analysis. Participants are also considering different cases of voltage drops across resistors in the context of the circuit's complexity.

  • #61
Femme_physics said:
Is the last term correct? I took this loop and I'm just unsure about the last term

Rather than simply answering, let me ask.
What are you unsure of?
Or rather, what do you need to be sure?
 
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  • #62
I'll take it as "you're right" :wink:

No, I'm not "unsure" anymore, I looked at it for a while and it makes sense now! :approve:
 
  • #63
Darn! I'll have to cloak my responses more carefully! :eek:
 
  • #65
You have a mistake in your second equation.

And I would suggest doing the math, because I think you have not practiced it enough.

Moreover, you have made the math harder for yourself because you took the entire enclosing loop instead of just the lower loop.
 
  • #66
I agree there is a mistake in the 2nd equation, but it may not be entirely mathematical.
It could be a conceptual one concerning voltage sources.

Taking the larger loop only adds one additional term versus the bottom loop.
Not a large enough difference in math to be concerned.
Either way results in 3 equations with 3 unknowns, which may be solved using
standard technique.
 
  • #67
The mistake is because I copied/pasted the first equation to the second equation to make the process of typing down the second equations easier, then I started deleting terms but I accidentally didn't delete the +12. It's just a typo type of mistake again, really
 
  • #69
Hey Fp! :smile:

I was wondering if I'd see you today.
And I can actually see you! :cool:

I see you worked the problem out carefully now.
And yes! It worked! You have the right answer! :smile:
How does it feel?

That leaves the second part of the problem...
 
  • #70
w00t! Thanks :smile:

Hmm my hair looks kinda too frizzly! :eek:


Wait before we get to the second part I want to ask a question from the test I had... I finally see I have a copy of the test so I can post it.. I think I'll start a different topic for that
 
  • #71
Well, the second part of the problem is almost trivial now.

I mainly attracted your attention to it, since in a real test, you should make sure that you do not forget to answer all the questions, just because you think you're done. :smile:
 
  • #72
I never heard the term "terminal voltage" before, though...can you tell me what it means?
 
  • #73
What do you think it means?
What could they mean?
Can you think of more than 1 interpretation?

(Often enough you'll get questions like this one where you more or less have to deduce what it is that they mean. :wink:)
 
  • #74
After a bit of googling :-p I know the answer!

Vt = 6 - I3r

:smile:

Right?
 
  • #75
I see you've used the tools at hand to "deduce" the meaning. Very good! :rolleyes:

Yes, that's the right formula.
Although on a test I hope you'll also give a numerical result. :smile:
 
  • #76
I will :smile: I'd be also very upset if during the test they wrote us something we hadn't studied like terminal voltage!
 
  • #77
Well, taking terminal voltage as an example.

Isn't it possible that they did teach it, but you missed it, forgot it, or perhaps you weren't attending when it was taught?
(Not that something like that would happen to you! )
Or perhaps the teacher making the test didn't realize that he was using a word that had not been taught.Still, if you can deduce its meaning on your own, you'll be able to answer correctly regardless of what happened!
(Much better imho than complaining that it wasn't taught! :smile:)
 
  • #78
Isn't it possible that they did teach it, but you missed it, forgot it, or perhaps you weren't attending when it was taught?

Why how dare you?!? Humphfh! Why I never!

Okay maybe I've ever'ed.

Or perhaps the teacher making the test didn't realize that he was using a word that had not been taught.

He hasn't use the word "internal voltage" in the problem! Just internal resistance, which is a whole other (SIMPLE) matter
 
  • #79
Pick two points and let me find the potential difference! :smile:
 
  • #80
GIANCOLI.ch26.p36.jpg


The 2 junctions. :smile:
 
  • #81
Vab = 12 -I2 x r -I2 x 11;
12 - 0.50842 x 1 - 0.50842 x 11

= 5.899 [V]

:smile:
 
  • #82
Right! :approve:
 
  • #84
*Protecting my eyes*

What? I can't C! :smile:

Show me yours and I'll show you mine. ;)
 
  • #85
Is this writing in codewords that I am correct? *grins*
 
  • #86
Yes, you're correct. :)

But, assuming the resistors blow up at the same amount of power, how much power must the resistors be able to withstand without blowing up?
 
  • #87
But, assuming the resistors blow up at the same amount of power, how much power must the resistors be able to withstand without blowing up?


:bugeye::bugeye::bugeye::bugeye::bugeye:

Uhhh...

Is that similar to the "max power" question? I really am lost as to how approach it.

Don't scare me before the test lol! :eek:

PS


Is the potential between A and B equals

Vab = E2 - I1 x R2 = 9 - 10.692 x 1 = -1.692 [V]
 
  • #88
Femme_physics said:
:bugeye::bugeye::bugeye::bugeye::bugeye:

Uhhh...

Is that similar to the "max power" question? I really am lost as to how approach it.

Don't scare me before the test lol! :eek:

Just kidding. :devil:
(And no, this one is much, much easier.)


Femme_physics said:
PS


Is the potential between A and B equals

Vab = E2 - I1 x R2 = 9 - 10.692 x 1 = -1.692 [V]

Yep! :smile:
 
  • #89
Phew! :smile:

Yep, think am ready^^
 
  • #90
Going back to the original circuit that started this topic,

If the directions of the currents weren't marked to me, how could I possibly have known it?
 

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