Wieght of discharged electronic capacitor or battery

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Discussion Overview

The discussion revolves around the weight of discharged electronic capacitors and batteries, exploring the implications of mass-energy equivalence and charge separation in capacitors. Participants examine theoretical aspects of mass changes related to energy states.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant suggests that discharged capacitors and batteries will weigh less due to reduced energy, referencing E=mc^2.
  • Another participant agrees, noting that mass-energy equivalence implies a decrease in mass when energy is lost, although they acknowledge the change would be negligible.
  • A different viewpoint highlights a misconception regarding capacitors, clarifying that charging does not change the total number of electrons, only their distribution, which may affect weight considerations.
  • One participant connects the concept to other systems, such as a wound-up spring, suggesting similar theoretical weight changes.

Areas of Agreement / Disagreement

Participants generally agree on the theoretical basis of mass-energy equivalence but express differing views on the implications of charge separation in capacitors and the practical detectability of weight changes.

Contextual Notes

Some assumptions regarding the detectability of mass changes and the implications of charge separation in capacitors remain unresolved. The discussion does not clarify the extent to which these theoretical considerations apply in practical scenarios.

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Am I right in assuming that an electronic capacitor and a battery will weigh less when discharged?
 
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It will have less energy when discharged, so theoretically, by E=mc^2 it will have less mass and therefore weigh less. However, the difference is so small you would be unlikely to detect it even with extremely sophisticated equipment.
 
Yes, it will. Just look at mass-energy equivalence.

Edit: Looks the Dale got it first.
 
Yes of course, thanks for that. I was thinking in the line of loss of electrons in capacitor and hence weight loss. I guess it follows from E=MC^2 that a wound up spring would theoretically weigh more also.
 
You are welcome, however I think you may have a misconception about what it means to charge a capacitor. When a capacitor is charged there is no net charge, instead there is only charge separation. A small number of electrons are removed from one plate and the same number of electrons is added to the other plate. The total number of electrons does not change, only their location.
 
Thanks, great forum.
 

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