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Homework Help: Three Kind of electrostatics problem(quite )

  1. Mar 18, 2008 #1
    Three Kind of electrostatics problem(quite urgent)

    1. The problem statement, all variables and given/known data
    The first kind of prbolem is about the dielectric coefficient
    http://myweb.polyu.edu.hk/~07190086d/phy/q1.zip

    I know the equations below
    but I don't know how to relate the E-field into eqn1
    The main reason is that I don't know is the D related in this kind of problem?


    2. Relevant equations
    Q1:
    (eqn1)
    [tex]\frac{tan\alpha1}{tan\alpha2}[/tex] = [tex]\frac{K1}{K2}[/tex]
    where alpha1 is incidence angle
    K is dielectric coefficient

    D=[tex]\epsilon[/tex]E
    where D is electric displacement
    E is E-field

    K=[tex]\epsilon[/tex]/[tex]\epsilon[/tex]o

    where [tex]\epsilon[/tex]o is the permittivity of dielectric
    [tex]\epsilon[/tex] is the permittivity of vaccum


    ===========================================================
    1. The problem statement, all variables and given/known data
    The second type of problem is about the simplest electrostatic problem!!!!!!!
    http://myweb.polyu.edu.hk/~07190086d/phy/q2.zip
    I don't really understand the meaning of "potential" is zero.
    Doesn't the potential is set by us?
    I know that when the net force is zero, then the PE should be minimum.
    But these problems make me very confusing.


    ===========================================================
    1. The problem statement, all variables and given/known data
    The last kind of question is about the leakage and capacitance.
    http://myweb.polyu.edu.hk/~07190086d/phy/q3.zip

    The equation related:
    RC=[tex]\epsilon[/tex]/[tex]\sigma[/tex]
    where [tex]\sigma[/tex] is lossy dielectric of conductivity

    I cannot really remember the previous concept of capacitance very well
    but I know that the time constant(decay to half ) is RC

    this problem are something new for me
    and I wanna know how to use the idea of lossy dielectric of conductivity
     
  2. jcsd
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