Spherical capacitor RC system -- determine steady state charges

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Homework Help Overview

The discussion revolves around a problem involving a spherical capacitor RC system, specifically focusing on determining the steady state charges. The original poster identifies the capacitance of a spherical capacitor and attempts to relate it to parallel plate capacitors, indicating a challenge in the problem-solving process.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the potential differences between spheres and infinity, and how to express these in terms of the capacitor's properties. There is an exploration of using the formula V=Q/C, with questions about the correct capacitance for a concentric shell capacitor.

Discussion Status

The discussion is ongoing, with participants sharing their approaches and expressing difficulties in progressing. Some guidance has been offered regarding potential differences, but there is no explicit consensus on a method or solution yet.

Contextual Notes

Participants are navigating the complexities of the problem, including the implications of using different capacitor models and the need for specific results or official answers. There is a noted uncertainty about the correct approach to take.

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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