Using Stokes law, calculate the work done along a curve

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SUMMARY

This discussion focuses on applying Stokes' Law to calculate the work done along a curve defined as the edge of a spherical triangle within the first octant of a sphere described by the equation ##x^2+y^2+z^2=R^2##. The vector field in question is ##\vec{F}=(z^2,x^2,y^2)##. Participants explore the parametrization of the triangle and the implications of using spherical coordinates for integration. The conversation emphasizes the importance of orientation in determining the sign of the integral results, particularly when applying Stokes' theorem.

PREREQUISITES
  • Understanding of Stokes' Theorem and its application in vector calculus.
  • Familiarity with vector fields and curl operations, specifically ##\nabla \times \vec{F}##.
  • Knowledge of spherical coordinates and their parametrization.
  • Ability to perform line integrals and surface integrals in multivariable calculus.
NEXT STEPS
  • Study the application of Stokes' Theorem in various contexts, focusing on vector fields.
  • Learn how to parametrize surfaces and curves in spherical coordinates.
  • Explore the significance of orientation in line and surface integrals.
  • Practice calculating curl and divergence of vector fields using examples.
USEFUL FOR

Students and educators in advanced calculus, particularly those studying vector calculus, as well as professionals working with fluid dynamics and electromagnetism who require a solid understanding of Stokes' Law and its applications.

  • #31
Wow, it feels so good to understand that! :D

So, the final sign, the result, basically depends on weather the ##r_{\phi }\times r_{\theta}## and normal vector determined by right hand rule match. If they do not, than the result must be multiplied by -1.

Please correct me if I am wrong.
 
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  • #32
skrat said:
Wow, it feels so good to understand that! :D

So, the final sign, the result, basically depends on weather the ##r_{\phi }\times r_{\theta}## and normal vector determined by right hand rule match. If they do not, than the result must be multiplied by -1.

Please correct me if I am wrong.
$$\pm\int_0^{\frac \pi 2} \int_0^{\frac \pi 2}(\nabla \times \vec F) \cdot \vec r_\phi \times \vec r_\theta~
d\phi d\theta$$
We are talking about the choice of the ##\pm## sign in the statement of Stoke's theorem. Whether the final answer of the problem is positive or negative is a different question and it depends on what the integrand is.
 

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