Find the outward flux of the field - Green's Theorem

In summary, the problem is to find the outward flux of the vector field F across the cardioid r=a(1+cos⁡θ), a>0. The solution involves setting up a double integral and determining the limits of integration. The limits are found by plugging in the equation of the cardioid, which is given in polar coordinates.
  • #1
mit_hacker
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Homework Statement



(Q) Find the outward flux of the field

F=(3xy-x/(1+y^2 ))i+(e^x+tan^(-1)⁡y )j

across the cardioid r=a(1+cos⁡θ), a>0.



Homework Equations



div F = (∂M )/∂x+∂N/∂y


The Attempt at a Solution



I could easily set up the double integral which is:

∬▒3 r^2 sin⁡θ dA

However, I am unsure as to how to determine the limits to be used.
Please help. Thank-you.
 
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  • #2
?? The limits of integration ARE the cardioid, of course: [itex]\theta[/itex] going from 0 to [itex]2\pi[/itex], r from 0 to a(1+ cos([itex]\theta[/itex])). Since that is given in polar coordinates, it might be best to convert div F to polar coordinates.
 
  • #3
Yes but...

Usually, the limits of r ranges from a constant value to another constant value of r. Why do we, in this case simply plug in the equation of the cardioid?

Thanks a lot for your help and support!:smile:
 

1. What is Green's Theorem?

Green's Theorem is a fundamental theorem in vector calculus that relates the line integral of a two-dimensional vector field over a closed curve to the double integral of the curl of the same vector field over the region enclosed by the curve. It provides a convenient way to calculate the circulation of a vector field and the outward flux of a vector field through a closed curve.

2. How is Green's Theorem used to find the outward flux of a vector field?

Green's Theorem states that the outward flux of a two-dimensional vector field through a closed curve C is equal to the line integral of the field along the boundary of the region enclosed by C. This means that the outward flux can be calculated by evaluating a line integral, which is often easier to compute than a double integral.

3. What are the assumptions for using Green's Theorem to find outward flux?

Green's Theorem can only be applied to a closed curve in a two-dimensional plane, and the vector field must be defined and continuous over the entire region enclosed by the curve. Additionally, the curve must be simple, meaning it does not intersect itself, and its orientation must be counterclockwise.

4. Can Green's Theorem be used to find the outward flux of any vector field?

No, Green's Theorem can only be applied to conservative vector fields, which have a curl of zero. This means that the outward flux can only be calculated for vector fields that satisfy the conditions of conservative fields.

5. Are there any alternative methods for finding the outward flux of a vector field?

Yes, there are other methods for calculating the outward flux of a vector field, such as using the divergence theorem or directly computing the double integral of the flux density function. However, Green's Theorem is often the most convenient and efficient method for calculating outward flux in two-dimensional cases.

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