Find the divergence of the function

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Discussion Overview

The discussion revolves around finding the divergence of a function, specifically in the context of vector calculus. Participants explore the gradient, curl, and divergence of vector fields, with a focus on spherical and cylindrical coordinates. The conversation includes homework-related queries and attempts at solutions.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant presents a function V and requests the divergence, curl, and gradient.
  • Another participant asserts that the formulas used are incorrect and emphasizes the need for proper notation.
  • There is a discussion about the necessity of unit vectors in expressing the gradient and the nature of curl and divergence.
  • Participants express confusion over the correct application of formulas and the use of unit vectors in different coordinate systems.
  • Some participants suggest using Wolfram Alpha to verify calculations related to gradients and divergences.
  • There are multiple attempts to clarify the divergence of specific vector fields, with varying degrees of success and correctness noted.
  • One participant questions the correctness of their formula and seeks confirmation from others.
  • Discussions include the importance of understanding the mathematical identities related to curl and gradient operations.
  • Participants also discuss the implications of using different coordinate systems and the need for careful application of divergence formulas.

Areas of Agreement / Disagreement

Participants generally express uncertainty about the correctness of their formulas and calculations. There is no consensus on the final answers, and multiple competing views on the correct approach and notation remain throughout the discussion.

Contextual Notes

Some participants mention confusion regarding the transition between different coordinate systems and the corresponding formulas for divergence and gradient. There are unresolved mathematical steps and assumptions regarding the use of unit vectors in spherical and cylindrical coordinates.

Who May Find This Useful

Students and individuals interested in vector calculus, particularly those working with divergence and gradient in various coordinate systems.

  • #31
DODGEVIPER13 said:
Hmm Bp/p isn't a derivative I am failing to see what I can do with this. I am going to go on a long shot here and guess that the unit vectors cancel as they multiply together, and p cancels the other p and leaves me with z^2 again? Then z^2+z^2 heh that can't be right, what am doing wrong anymore hints?

B = Bρ Uρ + ...
= ρz2 Uρ + ...

div B = ∂Bρ/∂ρ + Bρ/ρ + ...
= z2 + ρz2/ρ = z2 + z2 = 2z2

So you got it right, although I don't know exactly what you meant to say. You can see that the
ρ in the numerator and denominator of the second term do cancel.
 
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  • #32
ok will the rest of the terms work like this too?
 
  • #33
DODGEVIPER13 said:
ok will the rest of the terms work like this too?

You need to look up the general formula for the divergence in cylindrical coordinates. Then perform the indicated math.

Same goes for your C vector which is in spherical coordinates. You need to practice translating those general formulas into the specific expressions corresponding to your A, B and C.

It so happens that the Bρ component of div B is the only one that has a non-derivative term in it. This is true only for cylindrical coordinates.

When you get to taking the curl you need to be comfortable in using Cramer's rule to solve the appropriate determinant.
 
  • #34
ok my work is uploaded.
 

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