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B How many electrons on a Capacitor calculation

  1. May 16, 2016 #1

    ENE

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    Hello,
    How to find number of electronics in capacitor?
    as 1 coulomb and 1 Amp has 6.25x10^18
    on what they depend?
    Is this correct..?
    Q=C*V
    C=47uF and V=12V
    Q=47*10^-6*12=5.64*10^-4 Coulmb?????
     
  2. jcsd
  3. May 16, 2016 #2

    Drakkith

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    The number of electrons in a capacitor is given by Q=CV, which you've calculated correctly.
     
  4. May 16, 2016 #3

    ENE

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    Thanks.

    I don't understand this graph
    How the capacitor will charge with series Resistance?

    rc2.gif
     
  5. May 17, 2016 #4

    Drakkith

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  6. May 17, 2016 #5

    ENE

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    Hello,
    I got
    a. The rate of charging is typically described in terms of a time constant RC.
    b. The electrical transient phenomena in capacitors and inductors are exponential processes


    tcons.gif


    voltage across the capacitor
    how we get exponential here?
    rc15.gif
     
  7. May 18, 2016 #6
    The voltage on a capacitor is Vc = Q / C.

    Note: you copied images from two different circuit explanations and that's causing confusion. The "Vb" in the first image is "Vs" in the second image.
     
  8. May 19, 2016 #7

    ENE

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    i have to learn this equation?
     
  9. May 19, 2016 #8

    Vanadium 50

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    Oh, the horror! The horror!

    Yes, you have to learn it.
     
  10. May 19, 2016 #9

    ENE

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    in electrical engineering how man equation are there?
     
  11. May 19, 2016 #10

    jtbell

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    We solve the differential equation for the circuit. See for example

    http://web.mit.edu/molly/Public/circuits-b.pdf

    and scroll down to page W6-6. This uses Q as the variable, not V, but you can change variables using Q = CV if you prefer.
     
  12. May 19, 2016 #11

    ENE

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    Hello,
    Why The sum of the voltage drops∆Vi , across any circuit elements that form a closed circuit is zero.??
     
  13. May 19, 2016 #12

    ProfuselyQuarky

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    ENE, that's an awfully basic equation, you needn't worry :woot:
     
  14. May 19, 2016 #13

    Drakkith

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    The answer to this is kind of in-depth and I don't feel you're ready for it at the moment.
     
  15. May 19, 2016 #14
    The static electric field is a conservative field. So the work done on a closed path is zero.
    Do you understand the relationship between work and potential difference?
     
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