Finding the E field with a changing p?

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SUMMARY

The discussion focuses on calculating the enclosed charge (Qencl) when the charge density (ρ) varies with radius (r). The correct approach is to use the integral form Qencl = ∫(ρ*dV) when ρ is defined as ρ=ρ0r/R, indicating that ρ is a function of the variable radius. This method is essential for accurately determining the charge in three-dimensional problems, as opposed to the simplified formula Qencl = ρV, which is only applicable when ρ is constant.

PREREQUISITES
  • Understanding of charge density and its mathematical representation
  • Familiarity with integral calculus, specifically volume integrals
  • Knowledge of three-dimensional geometry in physics
  • Concept of variable radius in electrostatics
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  • Study the principles of electrostatics and Gauss's Law
  • Learn about volume integrals in three-dimensional space
  • Explore the implications of variable charge density in electrostatic problems
  • Investigate applications of charge density in real-world physics scenarios
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Physics students, electrical engineers, and anyone involved in electrostatics or charge distribution analysis will benefit from this discussion.

swimforever
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Finding the E field with a changing p?

Given that ρ=ρ0r/R when finding the charge enclosed would you use

1:Qencl = ∫(ρ*dV)

or

2: Qencl = ρV given that ρ has already been given with a coefficient to account for a changing r?
 
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If you mean that little 'r' is a variable radius then you must integrate (option 1), because the charge density is a function of the radius.

Integrate over a volume if the problem is 3dimensional, or over an area if the problem is 2d.
 

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