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Homework Help: How does a battery work?

  1. Jul 22, 2008 #1

    Sorry if this sounds blatantly obvious but I just wanted to clarify how a battery works. From my understanding, there are electrochemical reactions occurring within a battery that creates electrons on one end of the battery and thus a negative end. Subsequently, the other end is positive. My first question is, due to this charge differential, why can't the electrons just flow from the negative end to the positive end within the battery (I'm going to assume it can't simply because that would defeat the purpose of putting electrons on one end in the first place)? Now, if we connect a conducting wire to the two ends of the battery, what is actually going on - is the voltage created by the ends of the battery causing the conducting electrons of the wire to move to the positive end (towards a lower electrical potential energy)? Or is it that the electrons already on the negative end of the battery are traveling towards to the positive end through the wire? If it's the latter, are the electrons pushing each other one by one? Why can't an insulating wire work then if the source of electrons is from the negative end?

    Thanks a bunch!
  2. jcsd
  3. Jul 22, 2008 #2


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    Basicly, electrons at the negative electrode can be in one of two states:
    1. in a free, conductive state within the electrode material,
    2. bound to ions in a solution surrounding the electrode.

    To get to the positive electrode within the battery, they would have to travel through the solution. But in that case they are bound to ions, and a barrier within the battery prevents the ions from travelling (at least very much) between the two electrodes.

    It's all about chemistry, and involves the concept of enthalpy. Very simply, enthalpy is related to energy, but also depends on the concentrations of ions at the two electrodes.

    A system (such as a battery) favors a state of lower enthalpy, and it reaches that by two chemical reactions happening:
    1. a reaction at the negative electrode whereby ions give up electrons at the electrode,
    2. a reaction at the positive electrode, whereby ions receive electrons from the electrode.

    I think that the voltage difference is directly related to the enthalpy difference of these two reactions, but I'm not sure if that's strictly true.

    Others in here may be able to explain it better, but this is pretty much my understanding of things in a qualitative sense.
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