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Quick calculus help

  • Thread starter sm1t
  • Start date
6
0
1. Homework Statement

[tex]\nabla[/tex] of (r^-2)rhat x zhat

2. Homework Equations

[tex]\nabla[/tex](AxB) = B([tex]\nabla[/tex]xA) - A([tex]\nabla[/tex]xB)


Using cylindrical coordinates and curl in cylindrical with the above equation, I get zero?
But I think I am wrong?
Any help?
 

Tom Mattson

Staff Emeritus
Science Advisor
Gold Member
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I didn't get zero. Let's see what you did, then we can tell you where you're going wrong.
 
6
0
I am using the formula for curl in spherical, I konw I said cylindrical.
Taking the first cross product, zhat([tex]\nabla[/tex] x r^2 rhat) I use the ffact its in the rhat direction, so in the curl formula, sub r^2 for all r direction components. However they are then partially differentiated and I get zero, as the r^2 has no phi or theta components does it?
 

Tom Mattson

Staff Emeritus
Science Advisor
Gold Member
5,476
20
I am using the formula for curl in spherical, I konw I said cylindrical.
You should be using cylindrical. "z" isn't a spherical coordinate.
 

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