Energy of a charge configuration

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Discussion Overview

The discussion revolves around the energy associated with assembling a configuration of charges, particularly focusing on the assumptions made in classical electrodynamics regarding the process of bringing charges from infinity. Participants explore the implications of radiation during the assembly process and the theoretical nature of these assumptions.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions the validity of the assumption that charges can be brought in from infinity without considering the effects of radiation due to acceleration.
  • Another participant argues that the scenario is a mathematical construction and does not require practical consideration of radiation effects.
  • A later reply suggests that the energy associated with assembling a charge configuration can be represented by the Poynting vector, indicating a shift in focus towards electromagnetic energy flow.
  • Another participant emphasizes the importance of bringing charges in slowly and steadily to avoid radiation, framing it as a thought experiment that isolates the energy of the charge configuration from radiated energy.

Areas of Agreement / Disagreement

Participants express differing views on the necessity of addressing radiation effects in the assembly of charge configurations. While some view it as a theoretical construct that does not require practical resolution, others highlight the implications of radiation on energy considerations.

Contextual Notes

Limitations in the discussion include assumptions about the idealized process of charge assembly and the dependence on the definitions of energy and radiation in the context of electrodynamics.

zwoodrow
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Im rereading griffiths electrodynamics and noticed all the derivations of energy to assemble a given charge config assume you can bring charges in from infinity and stick them down. In reality if you tried this inevitable some of the particles would accelerate away or towards the incoming charge- they would radiate during acceleration - energy would go missing. How to deal with this.
 
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I don't understand - why do you need to 'deal with it'. It's a mathematical construction - a thought experiment.
It wouldn't be practical to actually assemble a charge configuration that way - you just pointed out why.
 
I just answered my own question- the energy released in assemble a charge or current configuration is represented bythe poynting vector.
 
A key to the idea, what AJ Bentley is talking about, is that you bring in the charges slowly and steadily such that they don't radiate energy. Its a thought experiment on what determines the energy of a charge configuration, radiated energy has nothing to do with it.
 

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