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Dielectric Strength

  1. Dec 5, 2009 #1
    I know it has to do something with the Breakdown voltage but i've looked everywhere on my book and i have no idea how to calculate it.
     
  2. jcsd
  3. Dec 5, 2009 #2
    i would reallly like to know, without this i can't do my problem.

    this is all i need.
     
  4. Dec 5, 2009 #3

    rock.freak667

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    What is the problem exactly?
     
  5. Dec 5, 2009 #4
    It's two parallell plates which 12 volts are applied, i already calculated the capacitance with the Area and distance between the plates. Now i must calculate it's dielectric strength.
     
  6. Dec 5, 2009 #5

    rock.freak667

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    The capacitance depends on the area, dielectric strength and distance. How did you find C with only two?
     
  7. Dec 5, 2009 #6
    Sorry, forgot to specify. i used the formula of

    C= eoerS/D

    where Eo is the permitivity constant, Er is the relative permitivity which was given in the exercise, S is the area of the surface and D is the distance between the plates.

    The Problem is which is the min. dielectric strength that it has.
     
  8. Dec 5, 2009 #7

    rock.freak667

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    but the dielectric strength depends on the fluid between the plates. The dielectric strength which is given by e0er
     
  9. Dec 5, 2009 #8
    What would the min. value?

    would i have to calculate a new er?
     
  10. Dec 5, 2009 #9
    and it doesn't specify the fluid, which is kinda of the point, for us to calculate it without looking at the table.
     
  11. Dec 5, 2009 #10

    rock.freak667

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    What you are doing sort of looks counter-intuitive to me.

    [tex]C=\frac{\epsilon_0 \epsilon_r A}{d}[/tex]

    you used that to get C, yes I get that. You know, A,d,ε0 and εr. You find C.


    What you are asking is to get ε (or ε0εr) for the same C, A and d. You will just get back what you used above. Am I missing something :confused:? Does A,d or A change?
     
  12. Dec 6, 2009 #11
    Exactly thats the formula but what im asked to calculate is the min. dielectric strength V/M.

    They give us Er which i looked up on a table and it's the Dielectric constant of Barium titanate.
     
  13. Dec 6, 2009 #12

    rock.freak667

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    V/M ? as in volt per metre as units? If that is the case then those units mean you need to find the electric field strength. Which is simply E=V/d
     
  14. Dec 6, 2009 #13
    Yep, it's positive right?
     
  15. Dec 6, 2009 #14

    rock.freak667

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    I would think so.
     
  16. Dec 6, 2009 #15
    The table in the back of my book that gives the different dielectric strengths it's unit is expressed x10^6 V/M and with that formula it only gives me kv/m.
     
  17. Dec 6, 2009 #16

    rock.freak667

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    What is the distance between the plates?
     
  18. Dec 6, 2009 #17
    2x10^-3 m
     
  19. Dec 6, 2009 #18

    rock.freak667

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    Well the dielectric strength gives the maximum electric field that can be applied before breakdown occurs. I doubt 12V is the maximum voltage, but that would be how to find it.
     
  20. Dec 6, 2009 #19
    Im in the crossroads in using this formula E= Q/EoArea that yields 7.2 x10^6 V/M or E= V/D that yields 6 kv/M

    A= 1m^2
    Q= 63.72 uC
    D= 2mm
    V= 12 V

    all the dielectric strength values in the table appear in x10^6 V/M
     
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