Determining an electric field in vector form, got the answer, just checking.

AI Thread Summary
The discussion focuses on calculating the electric flux through a surface with a given area vector and uniform electric fields. For the first scenario with E = 4i N/C, the flux is correctly calculated as 8 Nm²/C, derived from the dot product of the electric field and area vector. In the second scenario with E = 4k, the flux is 0 because there are no matching components in the area vector. The participants emphasize the importance of understanding vector components and the dot product in these calculations. Overall, the discussion highlights the significance of vector math in determining electric flux.
mr_coffee
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Hello everyone, I finally finished the chapter and now I'm going to attempt to do some problems. Well the first problem says: A surface has the are vector A = (2\hat i + 3\hat jm^2. What is the flux of a uniform electric field through it if the field is (a) E = 4\hat iN/C (b) E = 4\hat k. The answer for (a) is 8 Nm^2/C (b) 0. The answer is 8 for the first one because well (4)(2)...the j component isn't used at all because why? Also b is 0 because k isn't in the same vector as i or j, is that right or am i getting lucky?
 
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There's no j component for a. because the j component of the field you're given is 0. You're taking a dot product to find the flux, ie

\Phi_{E} = \vec{E} \cdot \vec{A}

So, when you evauluate that and you multiply the j components, you get 3 x 0 which is of course 0. That's the same reason that b. is 0, because \vec{A} has no k component and \vec{E} has no i or j components.
 
ohh! i forgot all about that, i have to refresh on vector math! thanks!
 
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