What happens to capacitance and voltage when a battery is disconnected?

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    Battery Capacitance
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Discussion Overview

The discussion centers on the behavior of capacitance and voltage in capacitors when a battery is disconnected. Participants explore the implications of this scenario, including the role of dielectric materials and the relationship between plate separation and voltage.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant notes that when a battery is disconnected, the charge remains on the capacitor plates, leading to an increase in voltage if the distance between the plates is increased, as described by the equation V=Ed.
  • Another participant questions how to find the electric field between the plates of a parallel plate capacitor, mentioning that the answer does not include distance.
  • A different participant raises a hypothetical scenario regarding infinite plates and whether the electric field would remain constant or fall off.
  • One participant references a video by Prof. Lewin that demonstrates how voltage increases when capacitor plates are separated, asserting that the electric field remains constant between the plates.
  • Another participant acknowledges the complexity of the topic and expresses openness to being wrong, indicating the challenging nature of the concepts involved.

Areas of Agreement / Disagreement

Participants express varying views on the behavior of the electric field and voltage in relation to plate separation, indicating that multiple competing perspectives exist without a clear consensus.

Contextual Notes

Some assumptions regarding the geometry of the capacitor and the nature of the dielectric are not explicitly stated, and the discussion does not resolve the mathematical relationships involved.

Who May Find This Useful

This discussion may be of interest to students and enthusiasts of physics, particularly those exploring concepts related to capacitors, electric fields, and the effects of dielectric materials.

FahimP
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hello i need some explanation on this .
I know that when a battery is connected it provides constant voltage across the capacitors. But the happens when the battery is disconnected. What happens to the voltage, the capicitance, and what is the importance of dielectric.

I have read the book the researched online but i can't seem to find an explanation on what happens when the battery is connected and when it is disconnected. PLEASE HELP
 
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When you charge up a capacitor and then disconnect the battery the charge is stuck on the plates . So if i increase the distance between the plates the voltage will go up. V=Ed
Because the electric field is constant between the plates . And the capacitance is only a function of geometry of the plates . And the dielectric allows more charge to be stored on the plates, and also so the plates don't touch each other.
 
Last edited:
In a parallel plate capacitor setup , If the distance is not to large the E field remains constant . I have a question for you, how do you find the electric field between the plates and the answer does not even have distance in it.
 
Suppose the plates where infinite, do you still think that the E field will fall off, or do you think it would be constant between the plates.
 

watch this video , Prof lewin explains capacitors and does a demo that shows the voltage will increase when you separate the plates. The E field is constant between the plates .
Start at about the 22min mark.
 
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No problem , I've been wrong many times, And its a very strange concept .
 

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