Magnitude of electric flux through a sphere?

Join the discussion
Registration is free. Start your own thread to ask a follow-up.
5 replies · 5K views
jlmccart03
Messages
175
Reaction score
9
****EDIT****: I had improper significant figures. It was the correct number.
1. Homework Statement

The electric field on the surface of a 6.0 cm -diameter sphere is perpendicular to the surface of the sphere and has magnitude 52 kN/C .

What is the magnitude of the electric flux through the sphere? Notice that the units of the answer involve kilo-Newtons.

Homework Equations


I = EA or I = E4pir2 = Q/epsilon

The Attempt at a Solution


I first attempted to try and use Gauss's Law, but didn't get as far as I had hoped since we are not given a charge as thought previously.

I then decided to us E*4pir2 to get 5881.06 kN *cm2/C which is 0.588106 kN*m2/C which is wrong. So I basically do not know how to approach this problem.

Thanks in advance for any help!
 
Physics news on Phys.org
The problem statement seems to be very incomplete because it doesn't say where the electrical charge is that is creating this electric field. You will get a different answer depending on the distribution of this charge. e.g. is it a surface charge, is it uniformly distributed throughout the sphere, or is there a point source at the center of the sphere?
 
Last edited:
Charles Link said:
The problem statement seems t be very incomplete because it doesn't say where the electrical charge is that is creating this electric field. You will get a different answer depending on the distribution of this charge. e.g. is it a surface charge, is it uniformly distributed throughout the sphere, or is there a point source at the center of the sphere?
My answer was correct, but was missing a few significant figures. I think in general it was just wanting us to use Gauss's Law on the most simplified version possible. Indeed it is incomplete, but that was everything the question gave me unfortunately.
 
  • Like
Likes   Reactions: Charles Link
Charles Link said:
The problem statement seems t be very incomplete because it doesn't say where the electrical charge is that is creating this electric field.
If the magnitude of the flux is uniform over the entire surface of the sphere then we can assume a spherically symmetric charge distribution that can be then be treated as a point charge located at the sphere's center.
jlmccart03 said:
My answer was correct, but was missing a few significant figures.
Strange, as I get quite different digits when I do the same calculation.
 
gneill said:
If the magnitude of the flux is uniform over the entire surface of the sphere then we can assume a spherically symmetric charge distribution that can be then be treated as a point charge located at the sphere's center.

Strange, as I get quite different digits when I do the same calculation.
Huh? Really? This is a screenshot of the question and answer.

upload_2017-1-30_17-42-49.png
 
  • Like
Likes   Reactions: Charles Link
My apologies. I mistook the diameter value to be a radius :oops: I hate when that happens :mad:

Anyhow, it's great that you arrived at the correct result. Cheers!