Direction of r-hat | Physics 2 Explanation

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Discussion Overview

The discussion centers around the determination of the direction of r-hat in the context of the Biot-Savart law, particularly as it relates to problems encountered in Physics 2 coursework. Participants seek clarification on the notation and conventions used in different textbooks and how these affect the interpretation of problems.

Discussion Character

  • Exploratory, Technical explanation, Homework-related, Debate/contested

Main Points Raised

  • One participant expresses confusion about how the direction of r-hat is determined, specifically in relation to the Biot-Savart law.
  • Another participant requests information about the textbook being used, noting that different textbooks may have varying notations and conventions.
  • A participant references a specific problem from an old exam, questioning the direction of r-hat for certain line segments.
  • It is suggested that r-hat should point from the current segment towards the point where the magnetic field is being evaluated, with a specific example indicating that a misdirection does not affect the final answer in that case.
  • One participant acknowledges the confusion caused by a similar problem in another test, where the labeling of r-hat was correct but still led to misunderstanding.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the direction of r-hat, as there are differing interpretations and experiences related to textbook conventions and problem-solving approaches.

Contextual Notes

Participants note that the direction of r-hat may vary based on the specific problem and the conventions used in different textbooks, which could lead to confusion in understanding its application.

Smooth23
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Okay, the biggest problem I'm still having 12 weeks into physics 2 is that I cannot for the life of me see how the direction of r-hat is determined. Can anyone explain it to me? Specifically in regards to Biot-Savart law, etc.
 
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Please tell us which textbook you're using. Different textbooks unfortunately use different notations and conventions for things like this. If you can show us the equations that you're looking at, someone who knows the subject well can probably figure out what's what.
 
Okay, I'm studying for a test, looking at former solutions here: http://campus.mst.edu/physics/courses/24/Old_exams/e3_spring2012_solved.pdf
number 7 has me confused for line segments 1 and 2 why is r-hat in the given direction?
 
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Okay, ##\hat r## is always supposed to point from the current (wire) segment ds towards the point P where you want to evaluate ##\vec B##. It's drawn backwards on segment 1. It should point towards P. It doesn't make any difference in the final answer because the contribution from segment 1 comes out zero either way.
 
Thanks, I realize it didn't make a difference in that particular problem. Another old test had a similar problem where it did make a difference, but was apparently labeled correctly that was really confusing the crap out of me.
 

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