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Is the positive terminal of a battery positively charged

  1. Aug 14, 2010 #1
    Hi

    If you are kind enough to answer this please bear in mind that I know next to no physics and I'm quite intimidated by the subject so please don't give me an intractable answer that I won't understand. Please feel free to answer as if you are talking to a nice but dim high school student.

    The question is in the title. I'm from a biological sciences background trying to learn about electricity. I've just learned a little about electric fields and electric potential and now I'm moving on to current electricity, starting with batteries.

    I've just read this:

    "Within the electrochemical cells of the battery, there is an electric field established between the two terminals, directed from the positive terminal towards the negative terminal. As such, the movement of a positive test charge through the cells from the negative terminal to the positive terminal would require work, thus increasing the potential energy of every Coulomb of charge that moves along this path. This corresponds to a movement of positive charge against the electric field. It is for this reason that the positive terminal is described as the high potential"

    I know this might be an obvious question but does this mean the positive terminal is actually positively charged and the negative terminal is negatively charged? (I have a vague recollection from redox reactions or something that sometimes its not what you would think it is but its so vague I can't remember)

    I have searched the forum for an answer to this question but I didn't understand it as it talked about capacitors and I don't know what they are

    Many thanks in advance
     
  2. jcsd
  3. Aug 14, 2010 #2
    Yes, there is a difference of charge distribution between the two poles, which causes the electric field. When you join the two poles with a conductor, the charges will "feel" this electric field and start moving in the conductor from the positive pole to the negative, thereby reducing the charge difference between the poles. The battery then consumes chemical energy to restore the charge difference, therefore maintaining the initial charge distribution, until the chemical energy finishes.
     
  4. Aug 14, 2010 #3
    That confuses me because I thought electricity was the movement of electrons and I thought a battery was something like this:

    Move electrons from A to B. This takes energy. This makes A positively charged and B negatively charged. The electrons at A have higher electric potential as they ahve been separated from 'their proton'. Electrons then move around the circuit from B to A to get back to the point of lowest electric potential.

    This comceptualistation is obviously flawed then???
     
  5. Aug 14, 2010 #4
    Yes, actually it's the negative charges that move. But that doesn't matter, as a negative current going one way is the same as a positive current going the opposite way.
     
  6. Aug 14, 2010 #5
    That sounds intuitive and I'm sure it makes sense but I can't quite see it. I think of charge as being an imbalance in the number of electrons and I can only visualise excess electrons moving. I can't get a picture for what positive current is. Can you help me with a model or analogy?
     
  7. Aug 14, 2010 #6

    Q_Goest

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    A battery does have a negative charge (surplus of electrons) on the negative terminal just as you'd expect, and the positive pole of a battery is positively charged (needs electrons to be in equilibrium).

    Convention has it that the flow of electricity is from positive to negative but that's not what actually happens. The flow of electrons is from the negative to the positive terminal. This convention of suggesting the 'flow' of electricity is from positive to negative is called "hole flow". There's an interesting http://everything2.com/title/hole+flow" that you might enjoy. Not sure if it's historically accurate but it seems pretty authoritative and I can vouch for the article's treatment of hole flow.
     
    Last edited by a moderator: Apr 25, 2017
  8. Aug 14, 2010 #7
    Is there actually an electric field inside a battery?

    Does a battery use energy to pump electrons to the negative terminal?
     
  9. Aug 14, 2010 #8
    Actually I will rewrite that question. Is there an electric field inside the battery? Is there an electric field outside the battery?

    I thought electrons were pumped against an electric field inside the battery and this did 2 things:
    1) it gave the electrons higher electrical potential
    2) created a positive and negative terminal

    but this means there is an electric field inside the battery and also between the terminals

    Have i got it wrong? Is it that electrons are moved inside the battery by a chemical reaction. This creates an electric field due to the charge separation
     
  10. Aug 18, 2010 #9
    I might be entirely wrong, but from what I understood of my electrochemistry class is that the charge is actually balanced on both electrodes, but because of the reduction potential, one of the the electrodes 'takes' electrons from the other electrode, and becomes reduced, while the other electrode oxidizes.
    I'm pretty sure there is no electric field inside a battery, even tho electric fields are used in capacitors.

    Electrons go from negative terminal to the positive.


    Hope that helps on something, dont take my word to be true, I just wrote what I inferred from classes.
     
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