MESH Current, Voltage Polarities

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Discussion Overview

The discussion revolves around understanding MESH Analysis, specifically focusing on determining voltage polarities across resistors in circuit loops. Participants seek clarification on methods for assigning voltage polarities and formulating MESH equations in a DC circuit context.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Homework-related

Main Points Raised

  • One participant expresses difficulty in determining voltage polarities across resistors while performing MESH Analysis and requests a detailed explanation.
  • Another participant suggests that the direction of assumed current flow determines the voltage polarities across resistors, indicating a conceptual understanding of the relationship between current direction and voltage polarity.
  • A different participant presents their approach to formulating MESH equations for two loops, expressing uncertainty about the correctness of their method and seeking feedback.
  • One participant acknowledges a basic misunderstanding and expresses gratitude for the clarification received regarding the concept of current flow and voltage polarity.

Areas of Agreement / Disagreement

Participants generally agree on the principle that the direction of current flow influences voltage polarities, but there is uncertainty regarding specific applications and methods for MESH Analysis. The discussion remains unresolved as participants continue to seek clarification and validation of their approaches.

Contextual Notes

Some participants express a lack of confidence in their methods, which may affect their ability to tackle more complex problems. There are also indications of missing foundational knowledge that could clarify the concepts being discussed.

tylercormier2
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Hello,

I'm trying to figure out MESH Analysis but for the life of me I can't seem to get the Voltage polarities on the resistors right. I usually like to assign my loop currents clockwise so I can get in some sort of a routine(I know it makes no difference). Can someone please help me explain the voltage polarities across resistors?

Here is a DC example,
http://www.art-sci.udel.edu/ghw/phys245/05S/examples/images/Mesh-ex1.gif

Can someone please explain to me a method for choosing voltage polarities in these loops and give the MESH equations? I think I am just missing something basic, so a detailed explanation would be nice.
Thanks
 
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tylercormier2 said:
Hello,

I'm trying to figure out MESH Analysis but for the life of me I can't seem to get the Voltage polarities on the resistors right. I usually like to assign my loop currents clockwise so I can get in some sort of a routine(I know it makes no difference). Can someone please help me explain the voltage polarities across resistors?

Here is a DC example,
http://www.art-sci.udel.edu/ghw/phys245/05S/examples/images/Mesh-ex1.gif

Can someone please explain to me a method for choosing voltage polarities in these loops and give the MESH equations? I think I am just missing something basic, so a detailed explanation would be nice.
Thanks

Please show us what you think they are first, and then we can comment. Them's the PF Rules.

Welcome to the PF!
 
Alright,

Here`s how I would approach this problem,
Left Loop : -9v + I1(5k) +(I1-I2)(6k)=0 (Clockwise Current Direction)
Right Loop: -9v - (I1-I2)(6K) + I2(12K) = 0 (Clockwise Current Direction)

I`m not sure if this is right or not, it`s what I came up with. I think my problem is I am not 100% confident in my methods which would lead me to mistakes on tougher questions. Anyways, I`d appreciate your input.
Thanks again.
 
The thing I'm getting stuck on is always hearing "The polarities within each loop for each resistor are determined by the assumed direction of current."
Can someone explain this concept for me please?
 
The part where current flows into to a resistor is more positive than where it leaves.

In mesh analysis, assume that current flows in a loop in some direction.
 
Ahhhhh. Thank you. Thank you soooo much. I knew it was something basic I was missing.
 

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