Why does an electric charge stop moving?

AI Thread Summary
An electric charge placed in an electric field will move until it reaches equilibrium, which occurs when the fields of the interacting charges have propagated sufficiently. If the charges are opposite, they will accelerate towards each other until they collide, forming an atom, while like charges will repel and continue to accelerate away, albeit with decreasing force. The discussion emphasizes the importance of the specific setup, as the behavior of charges can differ significantly between point charges and macroscopic objects. The apparatus may stop moving due to energy loss from emitting electromagnetic radiation, rather than reaching a static equilibrium. Overall, the details of the system are crucial for understanding why the charge stops moving.
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.
 
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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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