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Homework Help: Simple electric flux through tetrahedron problem

  1. Feb 1, 2012 #1
    A tetrahedron has an equilateral triangle base with 20-cm-long edges and
    three equilateral triangle sides. The base is parallel to the ground and a
    vertical uniform electric field of strength 200 N/C passes upward through
    the object.
    (a) What is the electric flux through the base?
    (b) What is the electric flux through each of the three sides?

    ATTEMPT:

    for part a i used flux=EA. for A i used BH/2 and got .0173. i multiplied that by 200 and got 3.46 m^2/C. can someone verify this is correct?

    for part b i just divided that number by 3 because the total flux in the sides must equal that of the base so i got -1.1533m^2/C. i think the sign is negative because it must have the opposite sign of the base. is this right?
     
  2. jcsd
  3. Feb 1, 2012 #2

    SammyS

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    I agree with the magnitudes.

    What is the convention for the sign of flux?
     
  4. Feb 2, 2012 #3
    the convention is positive sign?
     
  5. Feb 2, 2012 #4

    SammyS

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    For a closed surface, what direction is positive? Inward or Outward ?
     
  6. Feb 2, 2012 #5
    for a closed surface outward is positive
     
  7. Feb 2, 2012 #6

    SammyS

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    Good !

    Then the flux through the base is negative, correct?
     
  8. Feb 2, 2012 #7
    yes. and the sides are positive. thank you
     
  9. Apr 9, 2013 #8
    a) -3.464 Nm^2/C

    b) 1.2 Nm^2/C
     
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