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Potential in a capacitor

  1. Nov 24, 2004 #1
    how does the potential increases on adding positive charges and decreases on adding negative charges.
    why does the the existence of capacitor does not have any effect in a circuit with resistors and battery
     
  2. jcsd
  3. Nov 24, 2004 #2
    If you add charges, negative or positive, the potential difference between the plates of a capacitor increases. The reason is that always an equal charge of opposite sign in induced on a plate whenever you put a charge on another of the plates. So, since the ratio of charge and potential diff. is the constant ( and equal to capacitance ), the potential diff also increases.

    Existence of capacitors has an effect on the circuit. The current increses slowly and decays slowly etc.

    spacetime
    www.geocities.com/physics_all
     
  4. Nov 24, 2004 #3
    trouble

    I have got into trouble before for this reply -- it is however true.
    Potential is a very odd unit -- it is the amount of work done on a unit charge ( e.g. an electron ) in moving it thru an electric field from one place to another. the unit is therefore work ( joules ) per unit charge. specifically it is the work done in moving the unit charge from an infinite distance to the one under consideration. ( this is a precise definition )
    It follows that if you move more than one charge then the potential is proportional to the number of charges . ( it just takes more work )
    We have more misunderstanding of this unit than almost any other , because it envokes all sorts of images -- most of which are not true.
    for instance volts are NOT a force . potential is not like temperature
    there is NO absolute potemtial .
    Because there are many definitions of the volt ( to do with how it maybe measured ) it is a really confusing situation.
    However there is only ONE definition if you look at the units implied ( see dimensional analysis ) the basic metric is MKS -- meter kilogram second -- to which we have to ADD charge ( because it does not belong to the others ).
    This is why the measure of potential includes our normal metric but adds charge.
    What I am talking about here is the formal definition , NOT peoples idea of what this means . So take care and read up on any formal physics book for this definition.
    My personal advice is NEVER look up a 'forum' for definitions , they are full of peoples opinions which for the most part are innaccurate , and totally biassed -- any body who has the gall to call themselves a ' super mentor '
    should be shot !!!!!!!!!
    I do not know if this helps -- but it was a 'try'
     
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