# Coulomb's law with more point charges than one

• Lindsayyyy
In summary, the conversation discusses the concept of superposition and how it applies to calculating the force on a point charge. The participants also question why the interaction between particles 2 and 3 is not taken into account when calculating the force on particle 1. The concept of fixed charges and the usefulness of superposition in physics is also mentioned.
Lindsayyyy
Hi everyone,

I got a little question. Let's say we have 3 point charges on a line, for example on the x axis.

1----2----3

something like this. If I want to calculate the Force on point charge one, why am I allowed to just add the forces 12 and 13. I saw it in a book and was confused. Why don't I have to consider the interaction between the particel 2 and 3?

Lindsayyyy said:
Why don't I have to consider the interaction between the particel 2 and 3?
Why would the force that particles 2 and 3 exert on each other matter to particle 1? All you care about are the forces on particle 1.

if

1: -
2: -
3: +

I thought that 2 and 3 attract each other and the distance between 1 and 2 increases, because 1 and 2 repel aswell. Further distance -> force decreased. Or do I have to handle the charges like they are on a constant place? That's what I was wondering about.

You'll usually be given the locations of the charges. Assume they are fixed in place unless told otherwise. In any case, you are probably asked to find the force on particle 1 when the charges are in the locations given. If later they move, who cares? That's a different problem.

It's called superposition and its a wonderful thing as it makes calculation so much easier that can be applied in many aspects of physics.

Basically superposition says that each effect taken separately can simply be added togerther.

http://en.wikipedia.org/wiki/Superposition_principle

## 1. What is Coulomb's law with more than one point charge?

Coulomb's law with more than one point charge is a mathematical equation that describes the electrostatic interaction between multiple charged particles. It states that the force between two point charges is directly proportional to the product of their charges and inversely proportional to the square of the distance between them.

## 2. How do you calculate the force between multiple point charges?

To calculate the force between multiple point charges, you can use the following equation: F = k*q1*q2/r^2, where F is the force, k is the Coulomb's constant, q1 and q2 are the charges of the two particles, and r is the distance between them. The force will be repulsive if the charges are of the same sign and attractive if they are of opposite signs.

## 3. What is the direction of the force between multiple point charges?

The direction of the force between multiple point charges is along the line connecting the two charges. If the charges are of the same sign, the force will be repulsive and point away from each other. If the charges are of opposite signs, the force will be attractive and point towards each other.

## 4. Can Coulomb's law be applied to point charges of any size?

Yes, Coulomb's law can be applied to point charges of any size, as long as the distance between them is much greater than the size of the charges. This is because point charges are idealized particles with no physical size and the law assumes that the charges are located at a single point.

## 5. What are the limitations of Coulomb's law with more than one point charge?

Coulomb's law with more than one point charge is limited in its applicability to point charges only. It does not take into account the effects of the charges' motion or the presence of other nearby charges. Additionally, it assumes that the charges are stationary and do not create any magnetic fields. In reality, these limitations make the law less accurate for describing the behavior of real-world charged particles.

• Electromagnetism
Replies
18
Views
1K
• Electromagnetism
Replies
5
Views
923
• Electromagnetism
Replies
1
Views
700
• Electromagnetism
Replies
5
Views
2K
• Electromagnetism
Replies
2
Views
867
• Electromagnetism
Replies
14
Views
2K
• Electromagnetism
Replies
5
Views
1K
• Electromagnetism
Replies
7
Views
3K
• Introductory Physics Homework Help
Replies
21
Views
840
• Electromagnetism
Replies
5
Views
3K