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Electromagnetism - Linear charge

  1. Jun 1, 2017 #1
    1. The problem statement, all variables and given/known data

    cf48e17f857f9b75f951422f5b8d9171.png
    q=1.602*10^-19 point 1

    L=1mm=r1

    v=1.1*10^6 at point 2

    F=1.44*10^-12 at point 1

    2. Relevant equations
    E=(1/4πε)*(q/r)

    ΔV=∫E*dr=(1/4πε)*q∫(1/r)=(1/4πε)*q*ln (r2/r1)

    ΔU=ΔK=mv^2/2

    ΔK=mv^2/2=ΔV*q=q*(1/4πε)*Q*(ln(r2/r1))

    Q=F/E=1.44*10^-12/(q(4*pi*epsilon*(1.00*10^-3)^2))=1.00*10^-9

    3. The attempt at a solution


    mv^2/2=ΔV*q=q*(1/4πε)*Q*(ln(r2/r1))

    r2=0.002m

    IS this correct?
     
  2. jcsd
  3. Jun 1, 2017 #2

    gneill

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    Staff: Mentor

    Your problem statement doesn't actually state a problem. What is to be analyzed or found?

    What is the description of the scenario? Is that vertical charged rectangle meant to represent a short charged plate, part of in infinite plane of charge, a section through a disk of charge, or maybe just a short charged line segment? Something else?

    Please provide a complete problem statement.
     
  4. Aug 14, 2017 #3
    Sorry but you have to calculate the lenght from position 1 to position 2. It's an infinite linecharge.

    I can't understand where I went wrong in my calculations.
     
  5. Aug 14, 2017 #4

    rude man

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    Homework Helper
    Gold Member

    It's correct assuming v(L) = 0 and Q = line charge linear density which is usually written as λ and which has dimensions of QL-1, not Q.

    PS did not check math.
     
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