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How does a battery create potential difference

  1. Aug 19, 2013 #1
    i understand that the difference in potential energy creates an electromotive force that moves electron between the anode and the cathode, but what creates that potential difference at the -ve * real not conventional * anode of the circuit ?
    does the battery take the electron from the positive side and move it to the negative side ? i understand that both sides are separated inside a battery so i guess this is not possible .
    - is it the repulsive force caused by an excess of electrons on the negative side ?
    or is it that electrons that are produced by the chemical reaction with the anode have high energy * potential * which makes them go through the wire ?
    Last edited: Aug 19, 2013
  2. jcsd
  3. Aug 19, 2013 #2


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    A battery maintains a charge difference on the two terminals, in spite of the load (resitance in the circuit connecting the two terminals). The negative pole willl have a negative charge compared with the positive pole. The absolute charge on the terminals relative to some "neutral" reference depends on the circumstance, such as batteries connected in series.

    There's almost no chemical reaction in a battery until current starts to flow (the small amount of reaction is why a battery has a shelf life where it self depletes even without any external current flow). Once current is flowing, the chemical reaction tends to maintain the charge difference between the poles, although the charge difference and voltage will decrease somewhat as the load (currrent) increases.
  4. Aug 19, 2013 #3
    y still have not answered my question, how does the chemical reaction lead to a potential difference , is it by introducing electrons such that the repulsion increase and they start to flow towards the positive direction ? or by releasing high energy electrons that go back to their low energy-potential by flowing through the current ? i know the amount of electrons is somehow conserved , but what happens that make one end has more potential energy than the other ?
  5. Aug 19, 2013 #4


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  6. Aug 20, 2013 #5


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    Immersing a metal into an acidic solution it starts to dissolve. Positive metal ions from the surface of the metal go over to the liquid, leaving their electrons behind, and making the electrode negative. The ions stay close to the electrode, as it attracts them because of its negative charge, and some of them go back and become part of the metal again. A dynamic equilibrium is established at some potential difference between the ion cloud and metal. Some metals are more ready to dissolve than others, so immersed in the same electrolyte, they become more or less negative. Immersing two different metals in the same electrolyte, there is a potential difference between them, and connected by a resistor, current will flow. The current removes electrons from the more negative electrode, decreasing the attracting force they exert on the positive ion cloud, so some ions can migrate towards the other electrons and neutralize with the excess electrons arriving there through the load. At he same time, as the negative electrode becomes less negative, new ions dissolve and go over to the liquid phase, trying to maintain equilibrium potential difference between the electrodes.

    You can do experiments with two different metal pieces (steel and brass nail or screw, or two coins of different material) immersing them into slightly acidic liquid and measuring the voltage between them with a multimeter. You can also try inserting the electrodes into a lemon, apple or potato - they all will work.


  7. Nov 12, 2013 #6
    Ref bold highlighted quote:
    The term "electromotive force" was coined prior to full understanding of electrical science, it is not an accurate description. The emf is not an actual "force", per se, but a potential. The emf is not driving the electron or ion around the circuit.

    To learn about this process I would search under key words like "oxidation, reduction, half cell", and study battery action. Then you can gain some insight into this process. To explain how a battery maintains its terminal potential involves the topics I stated above. Some scholarly sources are what I recommend.

    I would visit a university site, chemistry dept., and hopefully batteries are covered. If not, maybe physics, chemical engineering, or electrical engr can provide explanations on battery action. I hope I helped.

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