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Homework Help: Potential difference between two points?

  1. Aug 15, 2010 #1
    This is a question from my highscool gr12 physics class
    Q) Two parallel plates are 8cm apart and are appositely charged. The electric potential difference across the plates is 160V. Point A is 2cm from the positive plate, point B is 3 cm from the negative plate.
    -What is potential difference between points A and B

    My attempt-
    Electric field intensity: E=[tex]\Delta[/tex]V/d = 160/0.08 =2000N/C
    [tex]\Delta[/tex]Va =E*d ---What value for d do i use?
    [tex]\Delta[/tex]Vb =E*d ---What value for d do i use?
    [tex]\Delta[/tex]Vab = [tex]\Delta[/tex]Vb - [tex]\Delta[/tex]Va
  2. jcsd
  3. Aug 15, 2010 #2
    because you're looking for potential difference you don't need to calculate the reference voltages at a and b independently. What if you just used
    E = d \Delta V
    straight from a to b?
  4. Aug 16, 2010 #3
    You don't need formulae, you can do it in your head.

    The plates are 8cm apart so at 160V there is a 20 volts per centimetre gradient between them.
    The points are 3 cm apart so the answer is 60 volts.
  5. Aug 16, 2010 #4
    thanks AJ, that makes sense to me
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