Question about batteries

Discussion in 'General Electronics Chat' started by Amaterasuu, Jun 16, 2012.

  1. Amaterasuu

    Thread Starter New Member

    Oct 10, 2010
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    Hello, I'm new to this material so please have patience.
    From what I understand, the anode of a battery is in a surplus of electrons.
    Since the cathode is in a deficiency, the electrons in the anode are attracted to the cathode (simplified a lot)
    Why do the electrons in the anode insist on going to the cathode in the first place? What would happen if I place a positively charged material(for instance, the cathode of another battery!) onto the anode of a battery, would the anode still unload the electrons?
    If so, how do connected batteries work? (connected in serial)
    Thank you for your time
     
  2. crutschow

    Expert

    Mar 14, 2008
    12,981
    3,221
    It's not particularly helpful to look at whether there is a surplus or absence of electrons at a particular battery electrode. The number of electrons really does not change at a battery terminal due to battery voltage, they just move from anode to cathode when an external circuit path is completed across the battery terminals.

    A battery generates a voltage (electromotive force) due to a electro-chemical reaction of the battery internal chemical compounds. This voltage will cause electrons to leave the anode (more negative terminal) and flow to the cathode (more positive terminal) when there is a complete external circuit from anode to cathode. If there is no complete circuit, the electrons just sit there (it's somewhat like the water in a pressurized pipe with the faucet closed). If you place two batteries in series (anode of one to cathode of the other) then the voltages of the two batteries simply add together. That's how higher voltage batteries are made -- for example a 12V auto battery consists of six separate cells in series.
     
  3. Amaterasuu

    Thread Starter New Member

    Oct 10, 2010
    9
    0
    First of all, thank you for the verbose reply.
    What I don't still get here however is the 'why'.
    People often compare batteries voltage with "height", both are indeed called "potential energy". But the gravitational potential energy has an abstract mathematical formula defining its value: m*g*h, where h is the height.
    Through this definition I can tell that the potential energy increases as height increases. That is why, if you lift 10 feet twice instead of once, you get more potential energy. (2h instead of h!)
    Question: Is there such a thing as a formula that would define the potential energy "generated" by two batteries in series?(or just one battery anyway) I believe the Ohm's law can't be applied here, but how else can people model the voltage between anode and cathode?
     
  4. #12

    Expert

    Nov 30, 2010
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    6,746
    The formula would be: 1+1 = 2

    What would you expect if you added 2 boxes of energy? 1 large box of energy? Well, that's what happens if you put 2 cells in parallel. Same "pressure", twice as much mass. Put them in series and you get twice as much pressure.
     
  5. WBahn

    Moderator

    Mar 31, 2012
    17,715
    4,788
    The battery takes charge at one end and "lifts" them from whatever potential they are add to a higher potential at the other end by electrochemical means. It is analogous to an elevator that lifts objects from one floor to another; if you have an elevator that lifts things 10ft, then an elevator at the ground floor would lift them from a potential of 0ft to a potential of 10ft while an elevator on the 10th floor would lift them from a potential of 100ft to a potential of 110ft. So to increase the potential of an object by 500ft, you would need not just 50 elevators, but 50 elevators placed in series so that each one lifts the object from the output potential of one elevator to the input potential of the next elevator. The same is happening when you connect batteries in series.

    Within the battery, the electrochemistry results in an electric field within the battery that is very analogous to a gravitational field.
     
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