Coulomb's Law: Maximum Force & Distance?

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Discussion Overview

The discussion revolves around the application of Coulomb's law to determine the maximum electric force between two charged objects and the corresponding distance when they are in contact. Participants explore the implications of charge properties, the nature of point charges versus real objects, and the specifics of measuring distances in practical experiments.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant suggests that the maximum force occurs when two charges are "stuck" together, questioning what the distance would be at that point.
  • Another participant argues that the distance should be defined as the distance between the centers of the two charged spheres when they are in contact, emphasizing that charge cannot be discussed in isolation.
  • A different perspective notes that Coulomb's law is typically applied to point charges, which do not have size, and thus, real charged objects require a more complex approach to account for their physical dimensions.
  • One participant shares an experimental scenario involving charged balloons, expressing confusion about measuring the distance between them when they are in contact and reiterating the assumption that it would be the distance between their centers.
  • Another participant confirms that measuring the distance between the centers is correct for spherically shaped charges, aligning with the context of the discussion.

Areas of Agreement / Disagreement

Participants express differing views on how to define the distance between charges when they are in contact, with some supporting the idea of using the centers of the charges, while others emphasize the need for a more nuanced understanding of real charged objects versus ideal point charges. The discussion remains unresolved regarding the best approach to measure distance in practical scenarios.

Contextual Notes

Limitations include the assumption that charges are spherically shaped and the dependence on the definitions of distance in the context of real versus idealized charges. The discussion also highlights the need for a more complex mathematical treatment when dealing with non-point charges.

Mohammed Alqadhi
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According to Coulomb's law, the electric force between two, equal in magnitude and opposite in direction, charges depends on the distance between them, and as they get close to each other, the force increases and the distance decreases. At the position when they get stuck with each other, the force will be maximum, but what would the distance be?
My approach is that it will be the distance between the two centers of the two charges, is that correct?
 
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Mohammed Alqadhi said:
According to Coulomb's law, the electric force between two, equal in magnitude and opposite in direction, charges depends on the distance between them, and as they get close to each other, the force increases and the distance decreases. At the position when they get stuck with each other, the force will be maximum, but what would the distance be?
My approach is that it will be the distance between the two centers of the two charges, is that correct?
Charge is property of bodies and particles, it does not exist by itself. You can not speak about the distance between charges.
If you have two charged spheres,and they get stuck, the distance between the centers is equal to the sum of the radii of the spheres.
 
Coulomb's law in the common form that you're using is for point charges, idealized objects with no size at all. Thus, no matter how close they are to one another, your charges won't touch and stick together.

Of course no real charged object is an ideal point particle; it has to have a surface and some size and shape. If you bring two of these close enough to touch, you'll have to use the more complicated integral form of Coulomb's law (google for "Coulomb's law integral") to calculate the force between them, and to do that you need to know the shape of both objects and how the charge is distributed within them.
 
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Actually, the experiment was two charged balloons brought to stick on each other after hanging them over a rod using two strings with the same length, and they also brought to be in an equilibrium condition, in which we found the electric forces using Newton laws. But, when I wanted to measure the charges on the balloons
(assuming they have equal charges) I got confused about the distance between them as they are stuck?
So, I assumed it will the distance between their centers.
 
Mohammed Alqadhi said:
My approach is that it will be the distance between the two centers of the two charges, is that correct?
Yes, that is correct for spherically shaped charges (which from context is what I believe that you are considering)
 
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