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Need help on an E&M problem

  • Thread starter taishar
  • Start date
  • #1
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I'm given this:

A vector field is given in cylindrical coordinates as:

F=(A)(s)(PhiHat) + (B)(z)(zhat)

Where A and B are constants. Could F be an electrostatic field ? Why or why not ?

I kind of feel stupid asking this because I feel like I should know, but, I'm currently braindead after having just spent hours doing the previous 29 problems.

Thanks,
Dan
 

Answers and Replies

  • #2
429
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taishar said:
I'm given this:

A vector field is given in cylindrical coordinates as:

F=(A)(s)(PhiHat) + (B)(z)(zhat)

Where A and B are constants. Could F be an electrostatic field ? Why or why not ?

I kind of feel stupid asking this because I feel like I should know, but, I'm currently braindead after having just spent hours doing the previous 29 problems.

Thanks,
Dan

an electrostatic field should be curl-less.

so... take the curl and see if it's zero or not.
 
  • #3
429
0
i guess i should provide some justification for my answer so that you'll believe me! :tongue:

an electrostatic field can be written in terms of a scalar potential:

[tex]
\mathbf{E} = -\nabla V.
[/tex]


and it is a mathematical fact that
[tex]
\nabla \times \nabla V = 0
[/tex]

for any V.


So if the curl is strictly zero, this implies that E can be expressed in terms of a scalar potential (and not have a vector potential term), and this is enough to determine if E is a static field or not.
 
  • #4
3
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Duh. I knew I was just being stupid. I had to do a couple similar problems earlier. Gah. Thanks a bunch :) Too many hours doing homework...
 

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