Curl of a field in spherical polar coordinates

In summary, the conversation is about finding the function wφ(r,θ) given the curl is zero and finding a potential for w. The conversation also includes a discussion about using the vector identities in curvilinear coordinates to solve the problem.
  • #1
Karacora
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Homework Statement


I have a field w=wφ(r,θ)eφ^ (e^ is supposed to be 'e hat', a unit vector)
Find wφ(r,θ) given the curl is zero and find a potential for w.

Homework Equations


I can't type the matrix for curl in curvilinear, don't even know where to start! I've been given it in the form ##\frac{1}{r^2 sin(\theta)}## multiplied by a determinant with top row:
er^, reθ^, rsin(θ) eφ^

Second row:
∂/∂r, ∂/∂θ, ∂/∂φ

Third row:
ar, raθ, rsin(θ)aφ

The Attempt at a Solution


ar, raθ = 0 and my aφ is wφ. So I'm left with

##\frac{1}{r^2 sin(\theta)}## ∂(wφrsin(θ)er^)/∂θ - ##\frac{1}{r^2 sin(\theta)}##(reθ^)∂(wφrsin(θ))/∂r

So I evaluated the partial derivatives, set each individual component to zero and get a partial differential equation. We have not been taught how to solve these, so I can only assume it's the wrong method... I gave it a go as the two equations are separable but they don't give w as a function of r and θ and I have no initial conditions to find c with!

After differentiating I had:
[rcos(θ)wφ + rsin(θ) ∂wφ/∂θ] er^ - reθ^ [sin(θ)wφ + rsinθ ∂wφ/∂r] all multiplied by ##\frac{1}{r^2 sin(\theta)}## And both components should individually equal zero, I think.
 
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  • #3

FAQ: Curl of a field in spherical polar coordinates

1. What is the definition of curl in spherical polar coordinates?

The curl of a vector field in spherical polar coordinates is a measure of the rotation or twist of the field at a given point in space. It is a vector quantity represented by a vector symbol (∇ x F) and can be calculated using the cross product of the gradient operator (∇) and the vector field (F).

2. How is the curl of a field calculated in spherical polar coordinates?

The curl of a field in spherical polar coordinates is calculated using a specific formula: (1/r) ∂(rFθ)/∂φ - ∂Fφ/∂θ + (1/rsinθ) ∂(rFrsinθ)/∂θ. This formula takes into account the changes in the field along the radial, azimuthal, and polar directions.

3. What is the significance of the curl in spherical polar coordinates?

The curl of a field in spherical polar coordinates helps to describe and understand the behavior of the field in terms of rotation and circulation. It is particularly useful in electromagnetism and fluid dynamics, where it can help determine the flow of electric currents or fluids in a given space.

4. How does the curl change with respect to the radius in spherical polar coordinates?

In spherical polar coordinates, the curl of a field varies with the radius. As the radius increases, the curl also increases, indicating a greater degree of rotation or twisting in the field. This is because the radial component of the field becomes more dominant as the radius increases.

5. Can the curl of a field in spherical polar coordinates be zero?

Yes, it is possible for the curl of a field in spherical polar coordinates to be zero. This occurs when the field is irrotational, meaning there is no rotation or twisting at a given point. In this case, the field can be described by a scalar potential function instead of a vector field.

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