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Explanation of capacitance formula

  1. Dec 2, 2014 #1
    Hello, I am new to electronics and am having trouble understanding this formula for capacitance:


    Could someone please break this down into layman terms? Interestingly π appears? I'd like to understand why that exists in capacitance.

    Thank you all in advance!
  2. jcsd
  3. Dec 2, 2014 #2


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  4. Dec 2, 2014 #3


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    Actually, that equation you got is very strange... 8.85*10^-12 looks like the value for vacuum permittivity (in F/m) in SI units, but I think that 4pi is wrong. Where did you get that equation?
  5. Dec 2, 2014 #4
    Thank you for the replies thus far. I got the image from this video at 1:05:
    I was wondering how I could make a capacitor from scratch. I am only up to pre-calculus so not entirely well-versed in mathematical reasoning yet.
  6. Dec 4, 2014 #5


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    Yes, I think he mixed up his units..


    ##C = ε * \frac{A}{d}##

    where ε is a constant. The form of the constant depends on the unit system used.


    He seems to have used the SI value for ε0
  7. Dec 4, 2014 #6


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    I think that's asking a bit too much. It's not a "layman's" subject. Unless you want to get into EM theory at some depth then it's quite OK just to use the formula (subject to it being the correct on - see the other posts. The nearest thing to helping you is to say that the Capacitance will be proportional to the total area (double the area = double the Capacitance) and inversely proportional to the spacing (double the spacing = half the Capacitance). The rest of the formula can be treated as 'just constants', which will give you the right answer in Farads. (I am not being snobby about this - many brilliant Engineers are prepared to do this and use formulas that they don't fully understand - in the same way that they used equipment that they could never hope to build for themselves)
    BTW π appears all over the place in Science and Maths. The bit about the area of a circle is only one of the many places you will find π - it is just the most familiar example :).
  8. Dec 7, 2014 #7
    Thank you all for the replies....I've got a lot to learn. I guess when in doubt consult wikipedia. π and phi and all constants are becoming particularly puzzling for me. For the sheer fact that a constant that relates to all things exists makes me think the universe was programmed...or the multiverse must be accurate. Sorry for being so tangential.
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