Electric field problem -- Repulsive force between two charged spheres

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SUMMARY

The discussion centers on the electric field problem involving two charged spheres that touch and then separate, resulting in a change in the repulsive force between them. The average charge after contact is calculated to be 2.5 nC, indicating that the charges equalize upon contact. The original charges of the spheres remain uncertain, and it is noted that the problem should specify that the spheres are significantly smaller than a 20cm radius to avoid complications in charge distribution due to their conductive nature.

PREREQUISITES
  • Understanding of electrostatics and Coulomb's law
  • Knowledge of charge distribution in conductors
  • Familiarity with the concept of electric fields
  • Basic principles of charge conservation
NEXT STEPS
  • Research the principles of charge equalization in conductive materials
  • Learn about the effects of charge distribution on electric fields
  • Explore the mathematical formulation of Coulomb's law
  • Investigate the implications of sphere size on charge interactions
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This discussion is beneficial for physics students, electrical engineers, and educators looking to deepen their understanding of electrostatic interactions and charge behavior in conductive materials.

Dezzi
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Homework Statement
Two identical spheres have charges q1 and q2. When they are 20 cm apart, the replusive force between them is 1.35×10^‐4N. After they touched together and separated once again to 20cm, the replusive force between them is 1.406×10^-4N. FIND q1 and q2. (Ans 20nC; 30 nC)
Relevant Equations
F=kQ1Q2/r^2
I attempt to solve the problem in the picture below.
 

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Why is the force different the second time?
 
PeroK said:
Why is the force different the second time?
The question say " they touched together and separated once again"
 
Dezzi said:
The question say " they touched together and separated once again"
So, what changed?
 
PeroK said:
So, what changed?
I guess the charges get equalised. So, you've worked out that average charge: ##2.5 nC##, which looks right.

The hard bit is to figure out what the original charges were. Any ideas?
 
A quibble: since the spheres are evidently conductors, the question ought to specify that the spheres are much smaller than 20cm radius. Otherwise the charge distributions complicate matters.
 
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