1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The integral

  1. Sep 25, 2009 #1
    1. The problem statement, all variables and given/known data

    Integration
    I am soooo lost. I don't even know if this is the right forum...... But where is the bridge between Calculus and Physics? I can Integrate equations, but when it comes to physics, i for one, don't know when to integrate; two, i don't see how you find the constants to remove from the integral; and three, Even given the integral formula for an equation, i still don't know what im doing. ?? finding the electric field of an object?? i thought Electric field was (1/4pi*epsilon naught)(Q/r^2). So how do i find the E field for different shapes?

    another example...

    ex. Va-Vb=SE.dl

    S-integral
    E-Electric Field
    dl-small segments of length

    I don't know how to use the equation;

    Or, electric flux,

    Flux=SE . dA

    What am i not understanding. Please help


    2. Relevant equations

    Flux=SE . dA

    Va-Vb=SE.dl



    3. The attempt at a solution
     
  2. jcsd
  3. Sep 27, 2009 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Welcome to PF!

    Hi Josh930! Welcome to PF! :smile:

    (have an integral: ∫ and a pi: and an epsilon: ε and try using the X2 and X2 tags just above the Reply box :wink:)
    Some physical quantities are A times B, or (vector) A dot B or A cross B …

    for example, work done = force times distance …

    if A and B are constant, then you just multiply, but if one or both is varying, then you have to integrate, eg: ∫A dB or ∫A.dB
    Do you mean the constant of integration? You choose it to fit the initial (or boundary) condition: eg, you might choose potential energy to be zero at infinite distance.
    To find E at position x for different shapes, basically you integrate ∫∫∫ Q(r - x)d3r/4πε0(r - x)3

    Va - Vb = ∫E.dl is the work-energy theorem: the LHS is the increase in PE, and the RHS is the work done … if E varies, then you need to integrate.

    And yes, electric flux = ∫ E.dA … what is worrying you about that? :smile:
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: The integral
  1. An integral (Replies: 2)

  2. Integration of (Replies: 10)

  3. Integral of (Replies: 3)

  4. Integral ? (Replies: 10)

  5. Integral of (Replies: 4)

Loading...