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Math Help - Flux

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    Flux

    I need to find the flux of the vector field F through S (in the pic), when S represent the edges of a cube.
    My question is, how do I find N (normal)? Do I need to split the curb and to find the flux through each face?
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  2. #2
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    Quote Originally Posted by asi123 View Post
    I need to find the flux of the vector field F through S (in the pic), when S represent the edges of a cube.
    My question is, how do I find N (normal)? Do I need to split the curb and to find the flux through each face?
    Yes. And you know the normal to each face, right?
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    Quote Originally Posted by mr fantastic View Post
    Yes. And you know the normal to each face, right?
    Is this right?
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    Quote Originally Posted by asi123 View Post
    Is this right?
    Yes.
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    Another thing, why the fluxes aren't canceling one another?
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    Quote Originally Posted by asi123 View Post
    Another thing, why the fluxes aren't canceling one another?
    Why should they cancel? The vector field is not constant ...... eg. For the flux through faces in the plane z = 0 and z = 1, F is different at those two faces .....
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    Still a bit stuck

    Lets say I want to calculate the flux which goes through the upper face.
    I know the vector field is F, and I know the normal, so I came up with this thing in the pic.
    My question is, how do I find ds?
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    I think I found a better way using Gauss' law, is this right?
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  9. #9
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    Quote Originally Posted by asi123 View Post
    Lets say I want to calculate the flux which goes through the upper face.
    I know the vector field is F, and I know the normal, so I came up with this thing in the pic.
    My question is, how do I find ds?
    For a cube:
    If you're in the plane z = a, dS = dx dy.
    If you're in the plane y = a, dS = dx dz.
    If you're in the plane x = a, dS = dy dz.


    Quote Originally Posted by asi123 View Post
    I think I found a better way using Gauss' law, is this right?
    Looks fine.
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