Electric field using Gauss' Law

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Homework Help Overview

The discussion revolves around calculating the electric field at the midpoint between two charged insulating spheres, one negatively charged and the other positively charged. The problem involves applying Gauss' Law to determine the electric field contributions from each sphere.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to use two Gaussian surfaces to calculate the electric field, questioning whether this method is appropriate. They express uncertainty about their calculations and the relevance of the spheres' radii.

Discussion Status

Participants are seeking more detailed information about the original poster's calculations and reasoning. There is a focus on ensuring that the problem is clearly stated and that the original poster provides sufficient detail for others to assist effectively.

Contextual Notes

The original poster initially did not specify the exact question being asked and has been prompted to clarify their approach and computations. There is an indication that the problem's setup may influence the solution.

cookiemnstr510510
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Homework Statement


Two small insulating spheres with radius 9.00×10−2m are separated by a large center-to-center distance of 0.545 m . One sphere is negatively charged, with net charge -2.35 μC , and the other sphere is positively charged, with net charge 4.35 μC . The charge is uniformly distributed within the volume of each sphere.
What is the charge at the midway point between charged spheres

Homework Equations


Gauss' Law: I will use ∫ for closed surface integral
∫E⋅dA=Qenclosed/ε0

The Attempt at a Solution


I used two gaussian surfaces. One encapsulating the negatively charged sphere and one the positively charged sphere. The radius of my gaussian surface was half the distance between the spheres, 0.2725m.
In gauss' law E can come out of the integral and the integral of dA is A.
Area of sphere is 4πr2
E4π(0.2725m)2=(2.35x10-6C)/(8.85x10^-12C2/Nm2)
This E will be pointing away from the negatively charged sphere at the midpoint between two charged spheres.

I did this for the positively charged sphere as well using a gaussian surface with the same radius(as above). I obtained an Electric field that this sphere contributes at the midpoint. I summed them up and got a total electric field. This answer is incorrect.
Not sure what I am doing wrong,
The problem gives the radius of both charged spheres so maybe this comes into play somewhere?
Thanks a bunch!
 
Last edited:
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How do you imagine that we will be able to help you if you do not show us what you did? You need to both describe it in words and show us all your computations. Otherwise it is just not feasible to find where you go wrong.

Edit: You also failed to actually specify what the question asks you to do. You just described the setup.
 
Orodruin said:
How do you imagine that we will be able to help you if you do not show us what you did? You need to both describe it in words and show us all your computations. Otherwise it is just not feasible to find where you go wrong.

Edit: You also failed to actually specify what the question asks you to do. You just described the setup.
I didnt write out all my calculations because I was more asking if the method was correct. What I mean is with a problem like this would drawing two gaussian surfaces, one around each charge, be a good place to start?
 
Orodruin said:
How do you imagine that we will be able to help you if you do not show us what you did? You need to both describe it in words and show us all your computations. Otherwise it is just not feasible to find where you go wrong.

Edit: You also failed to actually specify what the question asks you to do. You just described the setup.
Just fixed question, my bad.
 

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