# R_th wrong while applying series and parallel simple theory

• Ohmslaw
In summary, when simplifying the problem, I got a value of 700.745Ω, which was different from the answer in the solution which was 1.161KΩ. It's possible that my simplification from the perspective of R3 was incorrect.
Ohmslaw
Summary:: Trying to find Rth but I do not get the same value as the one from the solution.

[moderator: moved from a technical forum. No template.]

I am trying to find Rth to solve this problem, however once I simplified it, I get a value of 700.745 Ω while in the solution, the answer is 1.161kΩ. How is that possible ? What goes in parallel and what goes in series ?

Thank you !

Last edited by a moderator:
1. This looks like a homework question. It ought to be posted in that forum.
2. Is your simplification from the perspective of R3?
When I calculate the resistive network from the perspective of R3 it works out to 1.161K

It looks like you almost had it. My recommendation would be to move that ground so it's easier to interpret. Let's say we move it to where the V- is and draw the old ground as wires connecting to each other?

I'm not solving it for you... just redrawing it in a different way :) Would this be okay for you?

hutchphd, etotheipi, Asymptotic and 2 others
Ohmslaw said:
I get a value of 700.745 Ω

Based on your circuit diagram, it seems that you have found the equivalent resistance of the terminal (+) with respect to ground instead of the equivalent resistance of (+) with respect to (-).

hutchphd and Asymptotic
I believe the battery is drawn with positive ground.

Assuming the circle with the arrow is an amperemeter: R5 is in parallel with it, so it doesn't do anything. You get three parallel resistors and then R1 and the voltage source as separate elements.

That's a current source, I believe.

Suppress the sources and you get something like this:

Asymptotic said:
When I calculate the resistive network from the perspective of R3 it works out to 1.161K
Including R3, right?

hutchphd said:
Asymptotic said:
1. This looks like a homework question. It ought to be posted in that forum.
2. Is your simplification from the perspective of R3?
When I calculate the resistive network from the perspective of R3 it works out to 1.161K
Including R3, right?

That answer will include R3. I think a few people have answered this question :)

The phrasing seems odd to me. "From the perspective of R3" would seem to exclude R3 from the Thevenin. Semantics...

I agree: It makes R3 sound like the load. I solved it just to be sure.

hutchphd said:
The phrasing seems odd to me. "From the perspective of R3" would seem to exclude R3 from the Thevenin. Semantics...

"Perspective" was the first word that came to mind (at least, to my mind) that conveyed the essence of "Rth across R3".

Perspective, in the sense of "the combination of me, and all those connected to me". By that definition, network resistance from the perspective of R1 is 700.75Ω, from R3 is 1160.81Ω, and from R5 is 1361.02Ω.

Which is why we draw schematics! Worth more than a thousand words. Thanks.

## 1. What is the difference between series and parallel circuits?

In a series circuit, all components are connected in a single loop, which means the current passes through each component in sequence. In a parallel circuit, the components are connected in multiple branches, so the current can flow through each branch simultaneously.

## 2. How do I know if I've applied the series and parallel theory incorrectly?

If your calculations do not match the expected values or your circuit behaves differently than predicted, it is possible that you have made a mistake in applying the series and parallel theory. Double check your calculations and connections to ensure they are correct.

## 3. Can I mix series and parallel circuits in one circuit?

Yes, it is possible to combine series and parallel circuits in a single circuit. This is known as a combination circuit. However, it is important to properly calculate and analyze the circuit to ensure it functions as expected.

## 4. What happens if one component fails in a series or parallel circuit?

In a series circuit, if one component fails, the entire circuit will stop functioning. In a parallel circuit, the other components will continue to function, but the overall voltage and current may be affected.

## 5. How does the voltage and current change in series and parallel circuits?

In a series circuit, the voltage is divided among the components, so the total voltage across the circuit is equal to the sum of the voltage across each component. In a parallel circuit, the voltage across each branch is the same, but the total current is divided among the branches.

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