Spherical capacitor RC system -- determine steady state charges

AI Thread Summary
The discussion focuses on solving a problem involving a spherical capacitor and an RC system, emphasizing the use of the capacitance formula for a spherical capacitor, C = 4πε₀R. The initial approach of replacing spherical capacitors with parallel plate capacitors is deemed intuitive but leads to incorrect results. Participants are encouraged to derive expressions for the potential differences between the spheres and infinity, as well as between specific points labeled A, B, and C. The conversation highlights the importance of correctly applying the principles of electrostatics to achieve accurate results. Overall, the thread seeks guidance on the proper methodology for determining steady-state charges in the given system.
palaphys
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Homework Statement
Three uncharged metallic balls of radii a, b and a respectively are connected to terminals A, B and C with the help of long thin conductors as shown in the circuit. Find charges established on each of the balls, when a steady state is reached after the switch is closed. Consider the balls to be at great distances from each other as well from the circuit and neglect internal resistance of the battery.
Relevant Equations
Q=CV ,V=iR
1757832369543.webp

This is the diagram given for the problem.
Now I was able to identify, that the fact that the capacitance of a spherical capacitor, with one plate and the other at an infinite distance, is somehow to be used in this problem, i.e ##C= 4\pi\epsilon_0R ##

IF I can replace all the spherical capacitors with parallel plate capacitors with the same capacitance, I can solve the problem very easily. Though this seems intuitive, it yields the incorrect result.
Looking forward on how to approach this problem.
 
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palaphys said:
Though this seems intuitive, it yields the incorrect result.
Please post your result and the official result if known.
 
Three spheres.webp
Here is your approach. Look at the figure on the right. Each colored region of space encloses equipotential conductors in the steady state.

Start by finding expressions for the potential difference between each sphere and infinity. Then find expressions for the potential differences ##V_{AB}## and ##V_{BC}.##
 
Last edited:
kuruman said:
View attachment 365510Here is your approach. Look at the figure on the right. Each colored region of space encloses equipotential conductors in the steady state.

Start by finding expressions for the potential difference between each sphere and infinity. Then find expressions for the potential differences ##V_{AB}## and ##V_{BC}.##
let me try this
 
kuruman said:
View attachment 365510Here is your approach. Look at the figure on the right. Each colored region of space encloses equipotential conductors in the steady state.

Start by finding expressions for the potential difference between each sphere and infinity. Then find expressions for the potential differences ##V_{AB}## and ##V_{BC}.##
sorry, long time but I feel I've tried enough. not getting how to proceed. trying to use V=Q/C
 
palaphys said:
sorry, long time but I feel I've tried enough. not getting how to proceed. trying to use V=Q/C
Q is what you are looking for.
What is C for a concentric shell capacitor in which the outer shell has infinite radius?
 
palaphys said:
sorry, long time but I feel I've tried enough. not getting how to proceed. trying to use V=Q/C
I repeat:
haruspex said:
Please post your result and the official result if known.
And your working, of course.
 
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