Two spheres, solve for electric field strength

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Homework Help Overview

The problem involves calculating the electric field strength at the midpoint between two charged insulating spheres, one positively charged and the other negatively charged, with specific dimensions and distances provided.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the application of the electric field formula for spheres and attempt to calculate the total electric field strength at the midpoint. There are questions regarding the correct distances to use in the calculations, particularly the distance between the centers of the spheres.

Discussion Status

Multiple attempts at calculating the electric field strength have been shared, with some participants noting errors in their calculations and others suggesting careful attention to the wording of the problem and the distances involved. There is an acknowledgment of the need to correctly interpret the problem setup.

Contextual Notes

Participants are working under the constraints of homework rules, which may limit the information they can share or the methods they can use. There is a focus on ensuring the correct application of formulas and understanding the physical setup of the problem.

axgalloway
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Homework Statement


Two 2.0-cm-diameter insulating spheres have a 6.50 cm space between them. One sphere is charged to + 89.0 nC, the other to - 95.0 nC.

What is the electric field strength at the midpoint between the two spheres?


Homework Equations


Esphere = KQ/r^2
k = 8.99 * 10^9

The Attempt at a Solution



Esphere1 + Esphere2 = Etotal

(k*89*10^-9) / (3.25*10^-2)^2 + (k*95*10^-9) / (3.25*10^-2)^2
= Wrong answer: 1.57*10^6 N/C
 
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Nasty tricky wording!
Carefully sketch the spheres and mark all the distances clearly.
Remember the wording on that force formula: "distance between the centers of the charges".
 
Here was my 2nd attempt at a solution
Esphere1 + Esphere2 = Etotal

(k*89*10^-9) / (4.25*10^-2)^2 + (k*95*10^-9) / (4.25*10^-2)^2
= Wrong answer: 4.58*10^6 N/C
 
axgalloway said:
Here was my 2nd attempt at a solution
Esphere1 + Esphere2 = Etotal

(k*89*10^-9) / (4.25*10^-2)^2 + (k*95*10^-9) / (4.25*10^-2)^2
= Wrong answer: 4.58*10^6 N/C
Actually, that solution is a calculator error.
Here was my 3rd attempt at a solution (pressing the calculator correctly this time)
Esphere1 + Esphere2 = Etotal

(k*89*10^-9) / (4.25*10^-2)^2 + (k*95*10^-9) / (4.25*10^-2)^2
Correct answer = 9.16 * 10^5 N/C

Thanks for the help.
 
Last edited:

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