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Solving for distance between plates, diameter of a capacitor

  1. Mar 4, 2015 #1
    1. The problem statement, all variables and given/known data

    1. A 5.02 pF air-filled capacitor with circular parallel plates is to be used in a circuit where it will be subjected to potentials of up to 95 V. The electric field between the plates is to be no greater than 1.40×104 N/C. As an electrical engineer for Live-Wire Electronics, your task is to design the capacitor. What is its size? Enter the diameter and the separation of the plates.
    2. Relevant equations
    C=kEA/d
    E=V/d
    A=pir^2

    3. The attempt at a solution
    I used E=V/d to try and find the distance, then plugged that into the capacitance equation to find the area of the plates, which I then used to find the radius of the circle, which I multiplied by 2 to get the diameter.
     
  2. jcsd
  3. Mar 4, 2015 #2

    rude man

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    Homework Helper
    Gold Member

    Just what I would have done! Congrats!
     
  4. Mar 4, 2015 #3
    CAPA says my answers are wrong though! The answers I'm getting are 0.00679 for the distance between plates, and around 0.07 for the diameter..
     
  5. Mar 4, 2015 #4

    gneill

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    Staff: Mentor

    Did the system specify particular units to use? Is it finicky about significant figures?
     
  6. Mar 4, 2015 #5
    Well, apparently I was entering them in the wrong order..even though it says nothing about the order to enter them in. Thanks!
     
  7. Mar 4, 2015 #6

    rude man

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    Gold Member

    Well, I didn't check your math. I only endorsed your methodology! :smile:
     
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