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Homework Help: How does putting batteries in series increase voltage?

  1. Feb 24, 2013 #1
    1. The problem statement, all variables and given/known data
    When you put batteries you place the negative terminals to the positive which supposedly "bumps' each electron to the next battery. However, the positive terminal is positive enough to neutralize the negative terminal and vice versa. Therefore, when I place batteries in series, only the terminals connected to the load are supplying energy. The other terminals should just be neutralizing one another, yes?

    Even if the electrons are bumped along, how does it accumulate more voltage as it travels through the batteries?

    2. Relevant equations
    Please don't give me overly complicated equations. I'm only in grade 9.

    3. The attempt at a solution
    The only possibility I can think of is that the negative terminal has a greater charge than the positive terminal of the battery. In that case you would have electrons being "bumped along" but the number of "bumped" electrons would be (electrons in negative terminal)-(unneutralized protons in positive terminal), which wouldn't be very efficient.
  2. jcsd
  3. Feb 24, 2013 #2


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    There are no equations needed to explain this:

    You're getting hung up on "terminals" in a meaningless way. Just think of eliminating the two terminal that are touching and think of it as having built a bigger battery (that is, more plate, so more volts, not bigger plates so more current).
  4. Feb 27, 2013 #3
    Just to clarify, how does a battery really work in the first place? That's what's confusing me.
  5. Feb 27, 2013 #4


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    It's called a "battery" because it consists of multiple cells of this type:


    stacked together. Each cell produces a certain electric potential difference, and when the cells are combined in series to form a battery, their potentials add together. Same thing goes for combining two batteries (again, it's just a bunch of individual cells in series).
  6. Feb 27, 2013 #5


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    The amount of charge at the terminals of a battery is relatively small. When there is a load (completed circuit) placed on the battery, the internal chemical reactions will maintain some amount of charge on the terminals corresponding to the voltage versus load for that battery until the battery is depleted.

    In the situation where there is no external load and when you first connect the batteries in series, there is a very brief moment where the charge at the terminals results in a tiny amount of current flowing internally within the battery stack, but this only lasts for a brief moment while the internal chemical reactions compensate for a just connected series of batteries. Once a load is placed on the batteries, then the chemical reactions will create and sustain a current flow, and the voltage will equal the sum of the voltage of all the batteries in the series.
    Last edited: Feb 27, 2013
  7. Mar 3, 2013 #6
    Why would the current within the battery stack not be sustained for a long period of time? Does the resistance of an external path somehow offer an incentive for the electrons to travel through it?
  8. Mar 3, 2013 #7


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    If a battery could run forever without getting depleted it would be a perpetual motion machine. Nothing can provide power forever, it's just that batteries run out more quickly than some power sources, such as the sun.
  9. Mar 3, 2013 #8


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    Asuming you mean the case where there is no external load, then the current flows for just a brief moment while charges at the terminals and the chemicals inside reach a point of equlibrium. The charges on the internal terminals is essentially neutral, while the outer terminals retain negative and positive charges.

    When a load (completed circuit) is attached to the outer terminals, then the battery stack will maintain the charge corresponding to the voltage versus the load (current) for the outer terminals of the battery stack. The charges on the internal terminals will no longer be neutral, but transition from positive from the positive end of the stack to negative towards the negative end of the stack, again corresponding to the voltage and current flowing through the load and battery stack. During this time the potential energy inside the battery stack is being consumed in the form of a chemical transformation, eventually depleting the battery stack.
  10. Mar 16, 2013 #9
    So in a battery stack if I were to extract a cell from the middle it would have no charge because it would be neutral?
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