What does "stationary charges" mean in Coulomb's law?

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Discussion Overview

The discussion centers around the interpretation of "stationary charges" in Coulomb's law, particularly what it means for charges to be stationary in various contexts, including their motion relative to each other and to observers. The scope includes conceptual clarification and technical reasoning related to electrostatics.

Discussion Character

  • Conceptual clarification
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant asks whether "stationary" means charges are not moving with respect to each other, or if they can move together with a constant velocity.
  • Another participant states that if the charges are moving, one is no longer dealing with electrostatics and must use Maxwell's equations to describe the situation.
  • A participant questions whether an observer moving with the charges can apply Coulomb's law while another stationary observer cannot, suggesting a potential distinction based on relative motion.
  • It is noted that the situation is equivalent whether the observer and charges are at rest or moving, indicating a relativity aspect to the application of Coulomb's law.
  • One participant mentions that in many practical cases, velocities may be small enough to apply electrostatics as a good approximation.

Areas of Agreement / Disagreement

Participants express varying interpretations of what "stationary" entails, particularly regarding the roles of observers and the implications of motion. There is no consensus on a definitive interpretation of stationary charges, and the discussion remains unresolved.

Contextual Notes

Participants highlight the dependence on relative motion and the potential for approximations in practical applications, but do not resolve the implications of these factors on the definition of stationary charges.

Amio C
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Hello. I am an intro Physics student and this is my first post here.

In Coulomb's law the charges are said to be stationary. I need some clarification about what does it mean for two charges to be stationary:

A. Does it mean that the charges are not moving with respect to each other? (But maybe can move together with a constant velocity?)
B. Does it mean that the charges and the observer applying Coulomb's law has no movement compared to each other?
C. What if the charges and the observer all are accelerating at the same rate?

I am sorry if the answer is obvious. I would really appreciate your help.
 
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B. If the charges move you are no longer dealing with electrostatics and you will need the full set of Maxwell's equations to describe the electric and magnetic fields.
 
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Orodruin said:
B. If the charges move you are no longer dealing with electrostatics and you will need the full set of Maxwell's equations to describe the electric and magnetic fields.
Thank you for your answer. Please help me a bit more.
So if two charges along with an observer (let's call him / her "X") is moving at a constant velocity and another observer ("Y") is not moving; then "X" can apply Coulomb's law but "Y" can not - am I correct?
 
Amio C said:
Thank you for your answer. Please help me a bit more.
So if two charges along with an observer (let's call him / her "X") is moving at a constant velocity and another observer ("Y") is not moving; then "X" can apply Coulomb's law but "Y" can not - am I correct?

Yes - and of course this situation is equivalent to X and the two charges being at rest while Y is moving.
 
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Thanks to both of you. I understand it now.
 
This being said, it should be noted that in many of the cases you might deal with, velocities will be so small that you can apply electrostatics to a very good approximation.
 
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