Gauss's Law: Understanding kQ/r^2 in Point Charge Surroundings

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Discussion Overview

The discussion revolves around the understanding of Gauss's Law and the formula kQ/r^2 in the context of a point charge surrounded by a Gaussian sphere. Participants explore the implications of the formula, the nature of electric fields, and the visualization of field lines.

Discussion Character

  • Conceptual clarification
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether the electric field (E) on the surface of the Gaussian sphere is solely due to a single field line from the point charge and seeks clarification on the meaning of kQ/r^2.
  • Another participant asserts that field lines are a visualization tool and that the electric field exists everywhere, indicating that kQ/r^2 describes the field surrounding a point charge based on distance (r) and that the direction is radially outward for a positive charge.
  • A third participant explains that the electric field is constant on the Gaussian sphere because all points are equidistant from the charge, emphasizing that r^2 represents the squared distance from the charge.
  • A later reply suggests that kQ/r^2 can be understood as a result of the spreading of field lines, noting that the density of field lines correlates with the strength of the electric field, which weakens as 1/r^2 due to the distribution of field lines from the charge.

Areas of Agreement / Disagreement

Participants generally agree on the nature of the electric field surrounding a point charge and its dependence on distance, but there are nuances in understanding the implications of field lines and the formula kQ/r^2 that remain contested.

Contextual Notes

Some assumptions about the nature of field lines and their relationship to the electric field strength are not fully explored, and the discussion does not resolve the implications of visualizing electric fields through field lines.

ehabmozart
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Consider a point charge surrounded by a gaussian sphere. In the derivation of the formula, we said that E is constant everywhere on the sphere. Hence, we used Flux= EA.. However, isn't the E created on the surface is due to one field line out of the pint charge. I mean the formula kQ/r^2 is the field of the charge in a particular direction? I need clarification in this. Here, i just want to know kq/r^2.. What does it respond to?
 
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ehabmozart said:
However, isn't the E created on the surface is due to one field line out of the pint charge.
Field lines are just an aid to visualizing the field. The field exists everywhere.
I mean the formula kQ/r^2 is the field of the charge in a particular direction?
That tells you the field surrounding a point charge, which depends only on the distance r from the charge. The direction of the field is radially outward (for a positive charge).
 
The field due to the point charge is constant on the surrounding sphere because every point on that sphere is at the same distance away from the charge. You can think of r^2 as the (squared) distance from the point where the charge is to wherever you're measuring the field. Every point on the sphere has the same value of r^2 so E has the same magnitude at every point on that sphere.
 
yeah, I agree with these dudes. Another point: the kq/r^2 you can think of as a consequence of how the field lines are spreading out. The 'closeness' of the field lines is proportional to the strength of the electric field. And since the field lines are spreading out as 1/r^2 , then the electric field also weakens as 1/r^2. So in this way, you can think of the electric field as due to all the field lines coming out of the point charge, not due to any single field line.
 

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