Direction of r-hat | Physics 2 Explanation

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In summary, the biggest problem the speaker is having 12 weeks into physics 2 is understanding how the direction of r-hat is determined, specifically in regards to Biot-Savart law. They are using different textbooks which use different notations, making it difficult to understand the equations. The speaker is looking at former solutions and is confused about why r-hat is in a given direction for line segments 1 and 2. Another old test had a similar problem, causing confusion. However, it was labeled correctly and did not affect the final answer.
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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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  • #2
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.
 
  • #3
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 [Broken]
number 7 has me confused for line segments 1 and 2 why is r-hat in the given direction?
 
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  • #4
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.
 
  • #5
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.
 

What is the direction of r-hat?

The direction of r-hat is the unit vector that points in the direction of the displacement or position vector in a specific coordinate system.

What is r-hat used for in physics?

In physics, r-hat is used to represent the direction of a vector in a specific coordinate system. It is commonly used in calculations involving displacement, velocity, and acceleration.

How is r-hat calculated?

R-hat is calculated by dividing the vector by its magnitude. This results in a vector with a length of 1 and the same direction as the original vector.

What is the difference between r-hat and r?

R-hat represents the direction of a vector, while r represents the magnitude and direction of the vector. R-hat is a unit vector, meaning it has a length of 1, while r can have any magnitude.

Can r-hat change direction?

Yes, r-hat can change direction depending on the coordinate system being used. In a different coordinate system, the same vector may have a different direction of r-hat.

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