Why does an electric charge stop moving?

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Discussion Overview

The discussion revolves around the behavior of electric charges in an electric field, specifically addressing why an electric charge stops moving after being placed in such a field. The scope includes conceptual reasoning and theoretical exploration of electric fields, charge interactions, and equilibrium states.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants suggest that an electric charge will move until equilibrium is reached or until its field has propagated as far as another charge.
  • Others propose that if the charges are opposite, they will collide and form an atom, while like charges will accelerate away from each other indefinitely, though the magnitude of acceleration decreases with distance.
  • One participant emphasizes the importance of the details of the setup, questioning whether the discussion pertains to point charges or macroscopic charged objects.
  • Another participant notes that the propagation of the electric field is continuous and that the second field never truly stops propagating, as electromagnetic forces have an infinite range.
  • One contribution mentions that the apparatus would stop moving only if it loses energy through mechanisms such as emitting electromagnetic radiation.
  • There is a call for a clearer description of the system to facilitate understanding and discussion.

Areas of Agreement / Disagreement

Participants do not reach a consensus on why the charge stops moving, with multiple competing views and uncertainties remaining about the specifics of the system being discussed.

Contextual Notes

The discussion highlights the importance of specific details in the setup, as different configurations (e.g., point charges versus macroscopic objects) may lead to different behaviors. There is also a lack of clarity regarding the exact nature of the apparatus and the forces at play.

meesa
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If an electric charge is placed into an electric field of a charge that has been around for a while, it will start to move until equilibrium is reached, or until it's field has propagated out as far as the other charge. Note that the charges are connected by some non-conductive material.

Why/how does the charge stop moving?

Thanks.
 
Last edited:
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If the charges are opposite, they will both accelerate until they collide with each other and form an atom, which would be "equilibrium". If the charges are alike, then both will accelerate away from each other forever, with the magnitude of the acceleration dropping as the distance between the two charges increases, but never reaching zero.
 
The charges are connected. Forgot to put that originally.
 
We talking about point charges, IE electrons and protons, or about macroscopic objects that happen to be charged?
 
Two wires, two point charges, two things that are charged. This is for a final, and I'm having difficulty remember all the details of what was discussed, which is why I'm having trouble remembering why. I think the teacher did it with two wires connected to a non conductive material. After the first wire's field had propagated, the second wire was turned on. (No, this isn't in the book)
 
Unfortunately the details are important. Performing this experiment on two electrically charged wires in a laboratory is much different than two point charges in free space. If you'd like to, feel free to construct a specific scenario and ask about it.
 
It's all conceptual, and thus in space. All I need is why the apparatus stops moving once the second field has propagated. I'm sure the reason doesn't differ much depending on how the apparatus is designed in the conceptual world.
 
The 2nd field never stops propagating since the EM force has an infinite range while changes in the field propagate at a finite speed.
 
But the apparatus, which would begin to move in the time it takes for the second to propagate, would stop moving. I need to know how/why. I realize once it passes the other charged object it still keeps going.
 
  • #10
You're asking us to explain "how/why" before you have described "what". We can't do that - like Drakkith says, the details are important.
 
  • #11
The only way for the apparatus to stop moving, as far as I can tell, would be for it to lose energy by emitting EM radiation. Otherwise it would keep spinning or oscillating forever. It's hard to say since we don't have a specific setup.
 
  • #12
meesa said:
If an electric charge is placed into an electric field of a charge that has been around for a while, it will start to move until equilibrium is reached, or until it's field has propagated out as far as the other charge. Note that the charges are connected by some non-conductive material.

Why/how does the charge stop moving?

Thanks.

I don't understand why you think it would stop moving. The only thing to stop the object moving (in the absence of other forces, would be if the charges were opposite and they bump into each other.
As usual, a diagram would help a lot.
 
  • #13
Let's wait for the OP to describe the system. Completely describe the system. Guessing won't help him.
 

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