Finding the capacitance of two separated hemispheres

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SUMMARY

The discussion centers on calculating the capacitance of two adjacent hemispheres with radius R and distance d, each charged with ±Q. The participants highlight that the assumption of uniformly distributed charge does not yield equipotential hemispheres, complicating capacitance calculations. It is established that these hemispheres cannot be treated as standard conductors, which further complicates the definition and calculation of capacitance in this scenario. The lack of existing literature, such as Smythe's work, on this specific case indicates a gap in the theoretical framework.

PREREQUISITES
  • Understanding of electrostatics and capacitance principles.
  • Familiarity with the concept of electric fields and charge distribution.
  • Knowledge of equipotential surfaces and their significance in electrostatics.
  • Basic grasp of mathematical modeling in physics.
NEXT STEPS
  • Research the mathematical modeling of capacitance for non-standard geometries.
  • Study the implications of charge distribution on electric fields in electrostatics.
  • Explore advanced texts on electrostatics, particularly Smythe's work on capacitance.
  • Investigate numerical methods for solving complex electrostatic problems.
USEFUL FOR

This discussion is beneficial for physicists, electrical engineers, and students studying electrostatics, particularly those interested in advanced capacitance calculations and electric field theory.

jiajie
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Homework Statement
an interesting problem to discuss
Relevant Equations
How to calculate a pair of adjacent hemispheres capacitance?
like the picture, two adjacent hemispheres(radius R, distance d, assume the charge is ±Q of each side(assume evenly distributed), can we calculate its capacitance?
 

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What is the definition of capacitance?
 
The assumption of uniformly distributed charge doesn't lead to equipotential hemispheres. In this case, calculating the capacitance isn't an easy task.
 
Gordianus said:
The assumption of uniformly distributed charge doesn't lead to equipotential hemispheres. In this case, calculating the capacitance isn't an easy task.
They can't be conductors, so I don't think there is any standard definition of capacitance.
 
can we assume the electrical field is horizontally paralleled to simply it
 
jiajie said:
can we assume the electrical field is horizontally paralleled to simply it
Unfortunately, it isn't that simple. I checked whether Smythe had addressed this case but I had no luck.
 
Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

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