Point charge and electric flux

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SUMMARY

The discussion centers on calculating the electric flux through a sphere centered at a distance x from a point charge, where the sphere's radius is less than x. The key equation used is E*dA = (q_enc)/(e_0). Participants clarify that while the sphere does not enclose the charge, the net electric flux is not zero due to the nature of electric field lines intersecting the surface. The confusion arises from the misconception that q_enc must be zero when the charge is not enclosed.

PREREQUISITES
  • Understanding of electric fields and point charges
  • Familiarity with Gauss's Law
  • Knowledge of electric flux and its calculation
  • Basic grasp of Gaussian surfaces
NEXT STEPS
  • Study Gauss's Law in detail, focusing on applications to non-enclosed charges
  • Learn about electric field lines and their behavior around point charges
  • Explore examples of calculating electric flux through various Gaussian surfaces
  • Review the concept of enclosed charge (q_enc) in different geometrical configurations
USEFUL FOR

Students of electromagnetism, physics educators, and anyone seeking to deepen their understanding of electric flux and Gauss's Law applications.

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Homework Statement


You measure an electric field E at a distance x from a point charge. What is the electric flux through a sphere whose center is at that distance and whose radius is less than x from the charge?


Homework Equations


E*dA = (q_enc)/(e_0)


The Attempt at a Solution


I'm not sure that I'm understanding the question...The sphere does not enclose the point charge since its center is at x and its radius is less than x from the charge, so doesn't that mean q_enc = 0 and the flux is 0? (I have the answer so I know it's not zero, but I don't understand what I'm missing conceptually here...)
 
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net flux is 0
it means the new electric field lines crossing the total surface is 0
look at pic ... all field lines entering exit the Gaussian surface ! so net field through surface is 0
 

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channel1 said:

The Attempt at a Solution


I'm not sure that I'm understanding the question...The sphere does not enclose the point charge since its center is at x and its radius is less than x from the charge, so doesn't that mean q_enc = 0 and the flux is 0?
I believe that is correct.
(I have the answer so I know it's not zero, but I don't understand what I'm missing conceptually here...)
That's weird, what is the "correct" answer that you have been given?
 

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