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Stokes' Theorem

Relating circulation around a closed curve in space to the flux of the curl through any surface the curve bounds, whatever that surface's shape.

Active Calculus Multivariable, Stokes' Theorem

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4 exercises

Activity 13.13.3

  1. Find the circulation of F⃗=⟨3yz,xz,−xy⟩\vF = \langle 3yz, xz, -xy\rangle along the curve CC consisting of (given in order of the orientation) the quarter-circle of radius 11 centered at (0,−2,0)(0,-2,0) in the plane y=−2y=-2 from (0,−2,1)(0,-2,1) to (1,−2,0)(1,-2,0), the line segment from (1,−2,0)(1,-2,0) to (1,5,0)(1,5,0), the quarter-circle of radius 11 centered at (0,5,0)(0,5,0) in the plane y=5y=5 from (1,5,0)(1,5,0) to (0,5,1)(0,5,1), and the line segment from (0,5,1)(0,5,1) to (0,−2,1)(0,-2,1).

  2. Find the circulation of G⃗=3z2ı^−(z2+2x)ȷ^+zyk^\vG = 3z^2 \vi -(z^2 + 2x) \vj +zy \vk along the circle in the xyxy-plane of radius 33 centered at the origin. Ass…

2.5

Activity 13.13.4

Because Stokes' Theorem requires us to consider a surface (with normal vector) and the boundary of the surface, this activity will give you a chance to practice identifying the boundary of some surfaces in R3\R^3. For each surface below:

  1. Describe the boundary in words.
  2. Find a parametrization for the boundary.
  3. Ensure that a person walking along the boundary in the direction of your parametrization with hea…
2.5

Activity 13.13.5

In some sense, this activity considers the reverse problem of that considered in this activity. Here, each part of the activity gives you an oriented simple closed curve CC in R3\R^3, and your task is to find

  • a surface SS so that CC is the boundary of SS and
  • a normal vector for the SS so that a person walking along CC in the direction of the given orientation with head pointing in the direction of your chosen…
2.5

Exercise 14

Stokes' Theorem is generally used to turn a line integral into a flux integral. Sometimes it is possible to be given a flux integral and recognize that the given vector field F⃗\vF is curl⁡(G⃗)\curl(\vG) for some vector field G⃗\vG, however. When this is the case, we call G⃗\vG a vector potential for the vector field F⃗\vF, much like a function ff so that F⃗=∇(f)\vF = \grad(f) is called a potential function for F⃗\vF.

  1. Find a vector field F⃗\vF so that curl⁡(F⃗)=⟨x−y2,4xy−y−4,−4xz⟩\curl(\vF) = \langle x-y^2,4xy-y-4,-4xz\rangle.

  2. When f…

2.5

Adapted from Active Calculus Multivariable © 2013–2026 Nicholas Long, Mitchel T. Keller, and Steven Schlicker. Licensed under CC BY-SA 4.0. Source: Active Calculus Multivariable. Imported at revision 692c03c.