Direction of r-hat | Physics 2 Explanation

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SUMMARY

The direction of r-hat in the context of the Biot-Savart law is determined by pointing from the current segment (ds) towards the evaluation point (P) for the magnetic field (B). In the discussed problem from the Physics 2 course, the confusion arose from the incorrect drawing of r-hat for line segments, particularly segment 1, which was drawn backwards. However, this misrepresentation did not affect the final answer due to the zero contribution from that segment. Understanding the correct orientation of r-hat is crucial for accurately applying the Biot-Savart law in physics problems.

PREREQUISITES
  • Understanding of the Biot-Savart law
  • Familiarity with vector notation in physics
  • Knowledge of magnetic fields and their calculations
  • Ability to interpret physics problems and diagrams
NEXT STEPS
  • Review the Biot-Savart law and its applications in electromagnetism
  • Study vector calculus as it applies to physics problems
  • Examine various physics textbooks for different notations and conventions
  • Practice solving problems involving magnetic fields and current-carrying wires
USEFUL FOR

Students studying electromagnetism, particularly those preparing for exams in Physics 2, as well as educators and tutors seeking to clarify concepts related to the Biot-Savart law and vector notation.

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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