Does EMF Change During Battery Charging?

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    Battery Charging Emf
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Discussion Overview

The discussion revolves around whether the electromotive force (emf) of a battery changes during the charging process. Participants explore the implications of charging on the emf and the underlying chemical reactions involved, touching on theoretical and conceptual aspects of electrochemistry.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant questions if the emf of a battery remains the same before and after charging, seeking clarification on the charging process.
  • Another participant explains that charging a battery involves applying a voltage greater than the battery's emf to reverse the internal chemical reaction, suggesting that the emf does not change.
  • A follow-up response agrees that the emf remains constant while noting that the applied voltage converts to chemical energy.
  • Contrarily, one participant asserts that a battery's emf does change during charging and discharging, introducing uncertainty into the discussion.
  • Another participant expresses confusion about the reasons behind the potential change in emf, indicating a need for further explanation.
  • A later reply references Gibbs Free Energy and its dependence on ion concentration in the battery, suggesting that this relationship may explain changes in emf during charging.

Areas of Agreement / Disagreement

Participants exhibit disagreement regarding whether the emf changes during charging, with some asserting it remains constant while others argue it does change. The discussion remains unresolved, with multiple competing views present.

Contextual Notes

Participants reference concepts such as Gibbs Free Energy and the chemical reactions involved in battery charging, indicating that a deeper understanding of electrochemistry may be necessary to fully grasp the implications of emf changes.

vikcool812
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My doubt is that when we charge a battery we say that energy is transferred into it , but does the emf of a battery change in this process ? Is the emf same before and after charging , if yes then what actually happens during charging a battery ??

pls help !
 
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When you charge a battery, you apply a voltage greater than that of battery's in order to reverse the internal chemical reaction. The battery's emf is overcome by the voltage you apply to the leads.

The net result is a potential gradient large enough to reverse the chemical flow by pumping energy into the reactions. This is where the energy is stored.
 
so this means that the emf does not change , the extra potential applied just gets converted to chemical energy , did i get it right ??
 
The emf is the electromotive force. This is what pushes the electrons through the circuit and back to ground. Charging a battery sort of provides a bigger emf in the other direction, driving the current backwards. So while the battery is charging the total emf is the other direction but the emf provided by the battery remains the same.
 
A battery's emf does actually change as it is charged or discharged.
 
now i am a bit confused , even i think that the emf changes , but i am unable to figure out the reason , could someone just explane it . pls...
 
Hmm, it's been a while since I studied electrochemistry. I know it has to do with the change in Gibbs Free Energy (ΔG) for the chemical reaction involved, and ΔG depends on the concentration of ions in the battery solutions, which in turn depends on the charge state of the battery.

This site goes into it in detail, but assumes you are familiar with Gibbs Free Energy:
http://www.science.uwaterloo.ca/~cchieh/cact/c123/nernsteq.html

If nobody else can provide a better answer, I'll recommend you look at an introductory chemistry book (perhaps high school honors level, or college freshman level) that has a chapter devoted to electrochemistry. You'll need to be familiar with concepts like enthalpy and free energy, which would also be covered in such a book.

In particular, I can recommend the book Chemistry by Steven and Susan Zumdahl.
 
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