Magnitude of electric flux through a sphere?

AI Thread Summary
The discussion revolves around calculating the electric flux through a sphere with a given electric field. The initial approach using Gauss's Law was hindered by the lack of information about the charge distribution creating the electric field. Participants noted that the problem's statement was incomplete, as it did not specify whether the charge was on the surface, uniformly distributed, or a point source. One user corrected their earlier mistake regarding the sphere's diameter and confirmed their final answer was accurate but needed more significant figures. The consensus is that assuming a spherically symmetric charge distribution simplifies the calculation.
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 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 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!
 
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 'Variable mass system : water sprayed into a moving container'
Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...

Similar threads

Back
Top