Discussion Overview
The discussion revolves around Feynman's argument regarding the electric field inside a cavity of a conductor and its implications for electrostatic shielding. Participants explore the conditions under which the electric field is zero and the effects of grounding on this argument, addressing both theoretical and conceptual aspects.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- One participant references Feynman's argument that the electric field inside an empty cavity of a conductor is zero and suggests a similar argument applies to a cavity with charge, leading to a question about the implications for the electric field outside the conductor.
- Another participant claims that Feynman made a mistake, referencing comments by Thorne that challenge the validity of the argument presented in the lectures.
- A participant questions how grounding affects the argument, seeking clarification on the preservation of the argument under these conditions.
- It is proposed that if the conductor is grounded, a charge equal and opposite to that in the cavity can enter the conductor, potentially leading to a net charge of zero within a Gaussian surface surrounding the conductor, although it is noted that this does not necessarily imply the electric field must be zero.
Areas of Agreement / Disagreement
Participants express differing views on the validity of Feynman's argument, with some supporting it and others questioning its correctness. The discussion remains unresolved regarding the implications of grounding and the conditions under which the electric field is zero.
Contextual Notes
There are limitations regarding the assumptions made about charge distribution and the conditions under which the electric field is considered zero. The discussion also highlights the dependence on definitions of grounding and electrostatic conditions.
K. Now he says a similar argument can be used to show that if there is some charge in a cavity of a conductor than the field outside must be zero. Electrostatic shielding works both ways. Doubt: But then if we consider a gaussian surface containing the conductor , then the net charge is not zero => integral(E.da) is non zero, but E is zero. HOW?