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Homework Help: Potential Difference, given E

  1. Nov 1, 2007 #1
    1. The problem statement, all variables and given/known data

    What is the potential difference between yi= -5cm and yf=5cm in the uniform electric field E = ( 20,000{ i } - 50,000 { j } )V/m?

    2. Relevant equations

    ∆V = V(sf) - V(si) = -∫ Es ds

    with the limits of the integral being sf and si

    3. The attempt at a solution

    I tried doing the integral, resulting in (E2)/2, and then multiplying proceding as so:

    E= √ (200002 + 500002) = 53851.64807
    (E2)/2 = 14500000 = x
    x |0.05,-0.05 = -{x(0.05) - x(-0.05)} = -{2[x(0.05)]} = -1450000 = incorrect

    any help?

    thanks!
     
  2. jcsd
  3. Nov 1, 2007 #2
    I think you're taking the integral as if it were E dE instead of ds (Compare with the case where if it were the integral of x dx, then the integral is x^2/2). E is a constant since it is "uniform", so you can treat it as a constant and pull it out of the integral. If you're only dealing with one dimension (along y), then the integral of E ds simplifies to E(Sf - Si).
     
  4. Nov 1, 2007 #3
    aaahh lol nice....yea that was my mistake...lol whenever i see the integral sign i jump to conclusions without looking at the second part

    thanks!
     
  5. Nov 2, 2007 #4
    well actually...i tried that and it didn't work:

    E = 53851.64807

    Sf-Si = 0.05 - (-0.05) = 0.1

    E * (Sf-Si) = 53851.64807 * 0.1 = 5385.164807 = Incorrect :(

    Any help?

    Thanks!
     
  6. Nov 2, 2007 #5
    I have only one attempt left. I noticed that I didn't put the negative sign there, but the computer would tell me to 'check your signs' if this was a sign issue...so i assume it isn't
     
  7. Nov 3, 2007 #6
    any help?
     
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