Magnetic Field Surrounding a Straight Conductor

Click For Summary
The discussion focuses on understanding the derivation of the sine function in the context of the magnetic field surrounding a straight conductor. Participants clarify the relationship between the angles in the cross product ##\vec{ds} \times \hat r## and the angle ##\theta## depicted in a diagram. The connection is established through the definition of the cross product, leading to the equation involving sine functions. The clarification helps participants grasp the geometric relationships involved in the problem. Overall, the thread emphasizes the importance of understanding angles in vector calculations related to magnetic fields.
member 731016
Homework Statement
Please see below
Relevant Equations
Please see below
For this problem,
1673658720024.png

Part of the solution is,
1673658743775.png

1673658803501.png

However, would someone please tell me where they got the sine function circled in red from?

Many thanks!
 

Attachments

  • 1673658629770.png
    1673658629770.png
    8.2 KB · Views: 129
  • 1673658699232.png
    1673658699232.png
    35.2 KB · Views: 119
Physics news on Phys.org
Callumnc1 said:
However, would someone please tell me where they got the sine function circled in red from?
You're working with the cross product ##\vec{ds} \times \hat r##. How is the angle between ##\vec{ds}## and ##\hat r## related to the angle ##\theta## shown in diagram ##a##?
 
  • Like
Likes member 731016
TSny said:
You're working with the cross product ##\vec{ds} \times \hat r##. How is the angle between ##\vec{ds}## and ##\hat r## related to the angle ##\theta## shown in diagram ##a##?
Thank you @TSny ! I see how they got theta now. :) If we call the angle between ds and r hat as theta 2, then from the definition of the cross product:

dxsin(theta 2) = dxsin(pi/2 - theta) where I found theta 2 using angles in a triangle add up to 180 degrees.
 
Thread 'Chain falling out of a horizontal tube onto a table'
My attempt: Initial total M.E = PE of hanging part + PE of part of chain in the tube. I've considered the table as to be at zero of PE. PE of hanging part = ##\frac{1}{2} \frac{m}{l}gh^{2}##. PE of part in the tube = ##\frac{m}{l}(l - h)gh##. Final ME = ##\frac{1}{2}\frac{m}{l}gh^{2}## + ##\frac{1}{2}\frac{m}{l}hv^{2}##. Since Initial ME = Final ME. Therefore, ##\frac{1}{2}\frac{m}{l}hv^{2}## = ##\frac{m}{l}(l-h)gh##. Solving this gives: ## v = \sqrt{2g(l-h)}##. But the answer in the book...

Similar threads

  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 40 ·
2
Replies
40
Views
3K
  • · Replies 6 ·
Replies
6
Views
1K
  • · Replies 3 ·
Replies
3
Views
781
  • · Replies 20 ·
Replies
20
Views
3K
Replies
11
Views
3K
Replies
14
Views
3K
  • · Replies 21 ·
Replies
21
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K