Force that holds capacitor plates

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Discussion Overview

The discussion revolves around the forces acting on capacitor plates that are held at a constant potential difference by a battery. Participants explore the nature of the forces that maintain mechanical equilibrium of the plates, considering various factors such as dielectric materials and the physical setup of the capacitor.

Discussion Character

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

Main Points Raised

  • One participant notes that there is a force of attraction between the oppositely charged plates of a capacitor, prompting questions about the force that maintains their positions.
  • Another participant emphasizes that the plates are typically attached to a frame or surrounded by a material, suggesting that this setup contributes to their stability.
  • A participant raises a concern regarding the scenario where the dielectric is air and the connecting wires are weak, questioning the implications for mechanical equilibrium and energy changes in the system.
  • It is mentioned that while the electrostatic force is small, the plates will still move towards each other, with external factors like inertia and friction potentially affecting their motion.
  • A participant shares an experiential observation from an exhibit demonstrating the movement of charged threads, relating it to the behavior of capacitor plates.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the specific forces maintaining the mechanical equilibrium of the capacitor plates, and multiple viewpoints regarding the effects of different materials and configurations are presented.

Contextual Notes

There are unresolved questions regarding the impact of the dielectric material and the strength of the connecting wires on the mechanical stability of the capacitor plates, as well as the implications of energy changes in the system.

akhil123
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For any capacitor, whose 2 plates or conductors are being held by a battery to a constant potential difference of V volts, there is a force of attraction between the plates, since they are oppositely charged. What is the force that 'holds' these conductors at their respective positions i.e. what is the force that maintains mechanical equilibrium of each plate?
 
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akhil123 said:
What is the force that 'holds' these conductors at their respective positions i.e. what is the force that maintains mechanical equilibrium of each plate?
The capacitor plates aren't just floating in mid-air. They are usually attached to a frame or the space between them is filled with some material.
 
The dielectric slab will prevent the plates from collapsing onto each other...but what if the dielectric is air? And if the wires used to connect the conductors to the remaining circuit are weak copper strands? I am asking this because,when the net energy change for the (battery+capacitor) system is calculated when plates move nearer because of this attractive force, the total energy of the system decreases, and decrease of energy is always favourable for any system to achieve.
 
The electrostatic force is pretty small, but yes the capacitor plates will move towards each other. Depending on inertia, friction, air movement, etc, they may or not come into contact. At the Exploratorium in San Francisco we had a big box with two thread loops hanging from the top, one a bit shorter than the other so they couldn't "collide", you could charge up the threads with the same or opposite polarities of static electricity and watch them move.
 
Thanks a lot!
 

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