The effect of an external substance on the electric force between two charges

[hokhani]

How does the force between the two opposite charge change if we place a substance (conductor, insulator, ...) between them? It seems that the force between the two charges doesn't change but the total force on each charge increases because of the superposition of the original field of the other charge and the extra electric field due to the induced charge on the substance. I would like to know if I am wrong.

 

[mfb]

That depends on how you count the forces. What you described is one possible way to view the problem.

 

[hokhani]

That depends on how you count the forces. What you described is one possible way to view the problem.

If we had for example a thick wood between the two point charges, $q_1$ and $q_2$, can we say that:
the force between the two charges is $F=kq_1q_2/r^2$ and the resultant force (sum of the this force and the effects of other charges inside the wood) on each charge is zero? In other words, is the force between the two charges independent of any other effect?

 

[mfb]

and the resultant force (sum of the this force and the effects of other charges inside the wood) on each charge is zero?

Why would it be zero?

In other words, is the force between the two charges independent of any other effect?

That is one way to consider forces. It is not necessarily always the easiest approach.

 

[thierrykauf]

How does the force between the two opposite charge change if we place a substance (conductor, insulator, ...) between them? It seems that the force between the two charges doesn't change but the total force on each charge increases because of the superposition of the original field of the other charge and the extra electric field due to the induced charge on the substance. I would like to know if I am wrong.

If you put a conductor between two charges, doesn't the electric field vanish inside ?

 

[ZapperZ]

How does the force between the two opposite charge change if we place a substance (conductor, insulator, ...) between them? It seems that the force between the two charges doesn't change but the total force on each charge increases because of the superposition of the original field of the other charge and the extra electric field due to the induced charge on the substance. I would like to know if I am wrong.

Maybe you need to look at what happen to the electric field when you insert a dielectric in between the plates of a capacitor.

Zz.

 

[hokhani]

Why would it be zero?

I think a thick wood shields the electric field and so each charge doesn't feel the effect of the other charge.

 

[hokhani]

If you put a conductor between two charges, doesn't the electric field vanish inside ?

Right, It does. But I want to know the force between the two charges and compare it with the total force (the resultant force due to the two charge and the induced charge on the conductor surface) each charge.

 

[hokhani]

Maybe you need to look at what happen to the electric field when you insert a dielectric in between the plates of a capacitor.

Zz.

The main question is:
How does the force between the two point charges change if we put a conductor between them? (increase, decrease or no change)

 

[olgerm]

How does the force between the two opposite charge change if we place a substance (conductor, insulator, ...) between them?

conductor between the charges gets polarized.

 

[ZapperZ]

The main question is:
How does the force between the two point charges change if we put a conductor between them? (increase, decrease or no change)

Maybe you should re-read your own post. Here's what you wrote in the original first post:

How does the force between the two opposite charge change if we place a substance (conductor, insulator, ...) between them? It seems that the force between the two charges doesn't change but the total force on each charge increases because of the superposition of the original field of the other charge and the extra electric field due to the induced charge on the substance. I would like to know if I am wrong.

I simplified one part of the question by suggesting something that you can look up easily as an analogous situation. but I guess learning something is not what you're interested in.

Zz.

 

[hokhani]

Maybe you should re-read your own post. Here's what you wrote in the original first post:

Although the main question was about placing a conductor between the two point charges, I raised the question generally (for conductors and insulators and ...), and exactly stated what I like to know.

I simplified one part of the question by suggesting something that you can look up easily as an analogous situation.

My question is beyond the well-known dielectric effect which decreases the electric field between the two capacitor plates. This clear effect is explained exactly in the elementary textbooks.

but I guess learning something is not what you're interested in.

Please don't prejudice. Anyway, many thanks for your help.

 

[Lord Jestocost]

How does the force between the two opposite charge change if we place a substance (conductor, insulator, ...) between them?

No liability assumed. Your question is sometimes addressed in terms of an “effective distance between charges” in case a dielectric slab of a given thickness is placed in between two charges in vacuum.
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