Potential Energy system of 3 charged particles

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Discussion Overview

The discussion revolves around the interpretation of potential energy in a system of three charged particles, specifically addressing a test question regarding changes in potential energy values. Participants explore the implications of negative potential energy values and their relation to the ability to do work.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant expresses confusion over a test question regarding potential energy values of -200 J and -20 J, questioning whether the potential energy has increased or decreased.
  • Another participant challenges the reasoning that a higher negative value indicates greater potential energy, asking for clarification on the claim that the first system has a greater ability to do work.
  • A different participant asserts that both work and potential energy are scalars, suggesting that a higher magnitude in potential energy indicates a higher ability to do work.
  • Another participant counters that the sign of potential energy cannot be ignored, implying that the interpretation of potential energy must consider its negative value.
  • A participant later claims to have resolved their confusion, attributing their progress to the discussion, despite earlier disparagement.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of potential energy values, particularly regarding the significance of negative values and their implications for the ability to do work. The discussion remains unresolved with multiple competing interpretations.

Contextual Notes

Participants have not reached a consensus on the definitions and implications of potential energy in this context, and there are unresolved assumptions regarding the interpretation of negative values.

irishetalon00
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I simply can't wrap my head around a test question I received.

I'll relate it as best as I can remember:

"A system of 3 charged particles are arranged such that the total potential energy of the system is -200 J.
Then, consider the same 3 particles, arranged so that the potential energy of the system is -20 J.

Has the potential energy of the system decreased, increased, or stayed the same?"
The answer was : the potential energy increasesLet me explain why I'm stuck. Here's what I understand.

I understand that the number -200 is smaller than -20. If you look at it like that, then the answer is the energy of the system has increased.

But Potential energy = the ability to do work.

Considering that definition, the first system has the greater ability to do work, and thus has the higher potential energy, in which case the going from the first to the second system is a decrease in the ability to do work, and is therefore a decrease in the potential energy.

Your help is greatly appreciated, this question blindsided me and I feel like the timeline of my learning is on hold until I can overcome this hurdle!
 
Last edited:
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irishetalon00 said:
Considering that definition, the first system has the greater ability to do work, and thus has the higher potential energy,
Why do you say that?
 
I don't know! haha

Both Work and Potential Energy are scalars. So a higher magnitude in potential energy represents a higher ability to do work.

no?
 
No. Just because something is a scalar does not mean that its sign can be ignored.
 
I figured it out.

Thanks for the friendly and helpful response! :-p

Without your disparagement, no progress was possible!
 
irishetalon00 said:
Without your disparagement, no progress was possible!
:wink:
 

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