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Electric field in batteries

  1. Sep 4, 2015 #1
    Hello guys,

    It is said, that the battery differs from a capacitor when it is not connected to a circuit, by not having a seperation of charges. Its potential is due to a chemical process. My question is this chemical energy creates an electric field inside the battery? if no who creates it then?

    Thank you
     
  2. jcsd
  3. Sep 4, 2015 #2

    DEvens

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  4. Sep 4, 2015 #3
    I mean a normal battery the one we study in chemistry. It is said that the electrochemical potential is responsible for the current in a circuit. But when the battery is not connected to a circuit, there is still a potential due to the chemical energy. But my question is there any electric field inside the battery? if yes who is responsible for it?
     
  5. Sep 4, 2015 #4

    DEvens

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    Did you read the article I linked?
     
  6. Sep 4, 2015 #5
  7. Sep 4, 2015 #6

    DEvens

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    So, what do you conclude?
     
  8. Sep 4, 2015 #7
    I think there is no electric field inside a battery just the electrochemical potential right?
     
  9. Sep 4, 2015 #8
    A statement in the link says "When a battery is connected to an external circuit,Electrolytes are able to move as ions within, allowing the chemical reactions to be completed at the separate terminals and so deliver energy to the external circuit."
    My question is that what happens in electrolyte when it is connected to the load? Why does the chemical reaction only take place when the load is connected?
     
  10. Sep 4, 2015 #9

    CWatters

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    From that link...

    So during discharge electrons are needed at the anode. If the cell is open circuit (eg no load) there is no source of electrons so the chemical reaction stops.
    If the circuit is made these electrons come from the cathode via the load.
     
  11. Sep 4, 2015 #10
     
  12. Sep 5, 2015 #11
    If there is a potential difference between the electrodes, there is an electric field. You get the potential difference by intregrating the electric field along any path between the electrodes, inside or outside the battery. The only way to get rid of the field is to short out the battery.
    The electric field is produced by the chemical reactions that produce electrons on one side of the battery and consume them on the other side, these reactions produce a surplus of electons on one side and a deficit on the other and that is what produces the electric field.
    This electric field will eventually stop the chemical reactions. The movement of charges in the battery goes against the electric field. Connecting the electrodes and allowing a current to flow will lower the potential and the electric field and allow the reactions to proceed.
     
  13. Sep 5, 2015 #12
    Great, But why it is said that the battery when It is not connected to circuit, does not store charges like a capacitor?
     
  14. Sep 5, 2015 #13

    Drakkith

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    The amount of energy stored as chemical potential energy is vastly greater than the amount of energy stored as separated charges in a disconnected battery, so we say that a battery does not store charges like a capacitor does.
     
  15. Sep 5, 2015 #14

    Dale

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    The plates of a capacitor store a lot of charge with a very small separation with the energy being stored in the electric field and being highly dependent on the separation distance. The bulk dielectric polarises, but does not conduct and does not materially change during operation nor does it provide any net energy.

    The electrode of a battery store a negligible amount of charge with a very large separation with energy being stored in the chemical potential and being largely independent of the separation distance. The bulk electrolyte does not polarize, but does conduct and does materially change during operation and does provide net energy.

    There is, to my knowledge, no value in thinking of a battery like a capacitor.
     
  16. Sep 5, 2015 #15
    This Chemical potential produces electric field inside the battery ?
     
  17. Sep 5, 2015 #16

    Dale

    Staff: Mentor

    Yes. Usually it is called an EMF instead of an electric field.
     
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