How can Coulomb's Law be used to find the force between a charge and a surface?

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Homework Help Overview

The discussion revolves around applying Coulomb's Law to determine the force between a charge and a flat surface. The original poster presents a scenario involving a charge Q positioned at a distance h from the surface, seeking assistance with the calculation of the force exerted by the surface on the charge.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants explore the appropriate formulas for the situation, questioning whether the surface is conducting and discussing the implications of induced charges. There is mention of using Coulomb's force law and a reference to the method of image charges for analysis.

Discussion Status

The discussion is ongoing, with participants providing guidance on relevant concepts and techniques without reaching a consensus on the specific approach to take. The original poster's confusion about the formula and the nature of the surface remains a focal point.

Contextual Notes

There is an emphasis on understanding the conditions under which Coulomb's Law applies, particularly regarding the characteristics of the surface in question and the presence of induced charges. The original poster's request for help indicates a lack of clarity on these aspects.

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Homework Statement



We have a charge Q and it's h metres far from the flat surface. Find the force with which acts on the Q charge by the surface
The answer is: F=kQ2/4h2 i couldn't get it, please help me.

Homework Equations


The Attempt at a Solution

 
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shotikokobaxi said:

Homework Statement



we have a charge Q and it's h metres far from the flat surface. Find the force with which acts on the Q charge by the surface
The answer is: F=kQ2/4h2 i couldn't get it, please help me

Wow! No need to shout (Big loud font) :smile:

Welcome to Physics Forums, shotikokobaxi.

What formula(s) are appropriate here? Is the flat surface a conducting surface? If so, what analysis technique is appropriate for calculating the effects of an induced charge?
 
Last edited by a moderator:
gneill said:
Wow! No need to shout (Big loud font) :smile:

Welcome to Physics Forums, shotikokobaxi.

What formula(s) are appropriate here? Is the flat surface a conducting surface? If so, what analysis technique is appropriate for calculating the effects of an induced charge?

we use kulon's force F=kq2/r2 the question is to find the force with which the surface (which hasn't any charges) acts on the Q charge
 
shotikokobaxi said:
we use kulon's force F=kq2/r2 the question is to find the force with which the surface (which hasn't any charges) acts on the Q charge

Yes, that's what we call Coulomb's force law for electric charges. It is applicable, but there's a special technique which can be used for cases where one charge induces a charge in an otherwise uncharged conducting surface as you have here. Look up "the method of image charges".
 

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