Net flux through a closed sphere

AI Thread Summary
The net electrical flux through a closed sphere in a uniform electric field is zero because there is no charge enclosed within the sphere. This can be mathematically demonstrated using the first half of Gauss's Law, which states that the total electric flux through a closed surface is proportional to the charge enclosed. By visualizing the sphere with an axis aligned to the electric field and integrating the flux over area elements, particularly in a hemisphere, one can show that the contributions cancel out. The discussion confirms that this proof can be accomplished using single-variable calculus. Thus, the net flux through the closed sphere is indeed zero.
PeteyCoco
Messages
37
Reaction score
1
Find the net electrical flux through a closed sphere of radius R in a uniform electric field

I know that the flux is going to be 0 since there is no charge enclosed, but how would I show this mathematically? The next half of the question asks about a cylinder with sides parallel to the electric field, which I can prove is 0 easily, but I'm not sure if I know the math to prove the first scenario. Can the sphere-problem be proven with only knowledge of Single-Variable calc?

EDIT: I guess I'm asking if this can be proven easily using the first half of Gauss's Law, ignoring (Q-internal)/(epsilon-nought)
 
Last edited:
Physics news on Phys.org
Yes, it can be done with a single-variable integral.

You can visualize that the sphere has an "axis" aligned with the electric field. For area elements, take rings that are centered on that axis, something like this:
images?q=tbn:ANd9GcScKzbiYeomeocc55pBJpWhmYUKtXiqEEj4w3nIbxwtelBZndR1.png
Integrate the flux over all the area elements in a hemisphere, and you'll get that hemisphere's contribution to the total flux.

Hope that's clear enough.
 
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
Thread 'A bead-mass oscillatory system problem'
I can't figure out how to find the velocity of the particle at 37 degrees. Basically the bead moves with velocity towards right let's call it v1. The particle moves with some velocity v2. In frame of the bead, the particle is performing circular motion. So v of particle wrt bead would be perpendicular to the string. But how would I find the velocity of particle in ground frame? I tried using vectors to figure it out and the angle is coming out to be extremely long. One equation is by work...
Back
Top