point charge and electric flux


by channel1
Tags: charge, electric, flux, point
channel1
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#1
Feb5-11, 07:25 PM
P: 74
1. The problem statement, all variables and given/known data
You measure an electric field E at a distance x from a point charge. What is the electric flux through a sphere whose center is at that distance and whose radius is less than x from the charge?


2. Relevant equations
E*dA = (q_enc)/(e_0)


3. The attempt at a solution
I'm not sure that I'm understanding the question....The sphere does not enclose the point charge since its center is at x and its radius is less than x from the charge, so doesn't that mean q_enc = 0 and the flux is 0? (I have the answer so I know it's not zero, but I don't understand what I'm missing conceptually here....)
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cupid.callin
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Feb5-11, 09:59 PM
P: 1,135
net flux is 0
it means the new electric field lines crossing the total surface is 0
look at pic ... all field lines entering exit the Gaussian surface !! so net field through surface is 0
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Redbelly98
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#3
Feb6-11, 07:54 PM
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Quote Quote by channel1 View Post
3. The attempt at a solution
I'm not sure that I'm understanding the question....The sphere does not enclose the point charge since its center is at x and its radius is less than x from the charge, so doesn't that mean q_enc = 0 and the flux is 0?
I believe that is correct.
(I have the answer so I know it's not zero, but I don't understand what I'm missing conceptually here....)
That's weird, what is the "correct" answer that you have been given?


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