Gaussian surface and net flux

In summary, the conversation discusses the calculation of the net flux through five Gaussian surfaces, with the assumption that the charges enclosed by S1, S2, and S3 are equal in magnitude. The formula Φ= q/εo is used to determine the flux for each surface, with S4 having a flux of 0 due to the opposite charges of S1 and S2 canceling each other out. S5 has a flux of 2q/εo. The conversation also discusses determining the sign of the flux and finding someone to guide through the calculations.
  • #1
musicfairy
101
0
In the figure below, the charge on a neutral isolated conductor is separated by a nearby positively charged rod. What is the net flux through each of the five Gaussian surfaces shown in cross section? Assume that the charges enclosed by S1, S2, and S3 are equal in magnitude.

24_29.gif


Surface 1:

Surface 2:

Surface 3:

Surface 4:

Surface 5:



I don't know what to do, so I'll need someone(s) to guide me through the process.

I'm guessing I'll have to use the equations

Φ= q/ε0

I really don't know this stuff well, so I can't show much work as of now. That's why I'm trying to find someone who's willing to explain to me a step at a time.

First of all how do I know what sign it is? If it's negative does it mean the sign of q/ε0 is negative? Like S2 would be −q/ε0?

And for S4 would Φ = 0 because it contains S1 and S2 and they have opposite charges?
 

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  • #2
Figure that the net flux is the sum of the enclosed charge divided by permittivity.

So Φ= q/εo

So yes, S4 is 0 by the problem statement.

The others can be determined simply by using the formula.

I believe that S2 would be ΣΦ2 = -q/εo as stated.
 
  • #3
I think I get it now.

S1: Φ= q/εo

S2: Φ= −q/εo

S3: Φ= q/εo

S4: Φ= 0

S5: Φ= 2q/εo


Is this correct?
 

1. What is a Gaussian surface?

A Gaussian surface is an imaginary surface that is used in Gauss's law to calculate the electric field due to a charge distribution. It is a closed surface that encloses a certain amount of charge, and it can be any shape as long as it is closed.

2. How is a Gaussian surface related to electric flux?

A Gaussian surface is used to calculate the electric flux through that surface. The electric flux is defined as the amount of electric field passing through a given area. By using a Gaussian surface, we can simplify the calculation of electric flux by considering the electric field as constant over the surface.

3. Can a Gaussian surface be open?

No, a Gaussian surface must be a closed surface. This is because it is used to enclose a certain amount of charge and the electric field calculation relies on the symmetry of the surface. If the surface is open, the symmetry is broken and the electric field calculation becomes more complex.

4. How is net flux calculated using a Gaussian surface?

The net flux is calculated by taking the integral of the dot product of the electric field and the surface area element over the entire surface. This is given by the equation Φ = ∫E∙dA, where E is the electric field and dA is the differential area element. This integral can be simplified by using a Gaussian surface.

5. What is the significance of a Gaussian surface in Gauss's law?

A Gaussian surface is crucial in applying Gauss's law, which states that the net electric flux through a closed surface is equal to the total enclosed charge divided by the permittivity of free space. By using a Gaussian surface, we can simplify the calculation of the electric field and electric flux, making it easier to solve problems involving charge distributions.

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