Gauss's law

  • Thread starter sicrayan
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  • #1
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Homework Statement


An infinitely long insulating cylinder of radius R has a volume charge density that varies with the radius as given by the following expression where ρ0, a, and b are positive constants and r is the distance from the axis of the cylinder.
symimage.cgi?expr=rho%3Drho_0%28a-r%2Fb%29.gif

Use Gauss's law to determine the magnitude of the electric field at the following radial distances. (Use the following as necessary: ε0, ρ0, a, b, r, and R.)
(a) r < R
(b) r > R

Homework Equations


gauss's law
 

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Answers and Replies

  • #2
tiny-tim
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hi sicrayan! :wink:

show us what you've tried, and where you're stuck, and then we'll know how to help! :smile:
 
  • #3
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Hi
Thank you for your answer.
My unsuccessful solution:
lets take the length l,
for r<R,
WEyjR.png

why?
 
Last edited:
  • #4
tiny-tim
Science Advisor
Homework Helper
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hi sicrayan! :smile:

no, you're taking the mass inside radius r as πr2 times ρ(r) …

it isn't, you need to integrate :wink:
 

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