What is the electric flux through the top surface of the cube?

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SUMMARY

The electric flux through the top surface of a cube with a 3 nC point charge at its center is calculated using the formula φ = E.A, where E is the electric field and A is the area. The correct electric field at the top surface must account for varying distances from the charge, rather than assuming a constant field. The initial calculation incorrectly used a distance of 2.52, which led to an inaccurate electric field value. The correct approach requires integrating the electric field over the surface area to account for the varying distances.

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Homework Statement



A 3 nC point charge is at the center of 5 m x 5 m x 5 m cube. What is the electric flux through the top surface of the cube?

Homework Equations



E=kq/r^2
φ = E.A

The Attempt at a Solution



E = (8.99*109)(3*10-9) / 2.52 = 4.3152 N/C

φ = E.A = (4.3152)(5*5) = 107.88
But, it is wrong. Can someone please tell me what I am doing wrong?
 
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You assume a constant electric field over the whole top surface

The equation E=kq/r^2 where r is, I assume you put in 5, only the electric field at the center of the top. Every other point on the top is going to have a different r and electric field, it's not constant.

Edit: actually for r it looks like you used...sqrt(2.52)? I'm not sure where that came from
 
Last edited:

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