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Physics problems driving me crazy- each book has different formulas

  1. Apr 25, 2013 #1
    1. The problem statement, all variables and given/known data
    The electric potential difference between two parallel metal plates is delta V. The plates are separated by a distance of 3 .0 mm and the electric field between the plats is E = 250 V / m. Calculate delta V


    2. Relevant equations

    E = - delta V / delta D

    3. The attempt at a solution

    250 V / m = - 120 V / D

    D = -0.75 V

    The answer says 0.75 V.

    Is it positive or negative? can someone help?

    The prior question I solved, using this formula and plugging in values gave me -1.2 * 10^3 N/C.

    So, why is it positive? Thanks
     
  2. jcsd
  3. Apr 25, 2013 #2

    ehild

    User Avatar
    Homework Helper
    Gold Member

    "Electric field between the plates" does not specify the direction of the field. It points to the lower potential. Calculate with the absolute values. A distance is always positive.

    ehild
     
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