# Where is the neutral point? Electrostatics

• rize
In summary, at the neutral point between two point charges of +2nC and -3nC separated by 2.0m in air, the electric field intensity is zero. The distances from the neutral point to each charge, d1 and d2, can be calculated by setting the electric field equations for each charge equal to each other and solving for d. This will result in a quadratic equation with two solutions, representing the two neutral points. Using the rules of repulsion/attraction for charges, it can be determined that the neutral point will not be between the two charges, but rather to the left of the negative charge. The distance from the neutral point to the positive charge is d1, and the distance from the

## Homework Statement

At the neutral point the electric field intensity is zero. Two point charges q1=+2nC and q2=-3nC are separated by 2.0m in air. Where is the neutral point?

E=f/q
coloumbs law
E=E[q1] + E[q2]

## The Attempt at a Solution

i don't have a solution for now since i can't figure out how to solve for d1 and d2

i don't have a solution for now since i can't figure out how to solve for d1 and d2

What are $$d_1$$ and $$d_2$$ ??

d1 is the distance of q1 from the neutral point , d2 is the distance of q2 from the neutral point

Just try to look at it like a 1D problem. Along a line joining the two charges there will be a point where the sum of the fields is 0. Also using rules of repulsion/attraction for charges, you can figure out that the point will NOT be between the two charges. So the distance from one charge is d1, and the distance from the second charge is 2+d1.

Drawing a picture always helps. :)

rize said:
d1 is the distance of q1 from the neutral point , d2 is the distance of q2 from the neutral point

Just take it as 'd' from q1. Once you calculate distance from q1, you can use your math to get the distance from q2.

Actually, in this case there will be two neutral points. So you'll get a quadratic equation.

Code:
           *                 q1-------------------------------q2          *
Code:
             |<----------->|
d

* is neutral point.
$$E_{q1}=E_{q2}$$
$$\frac{k*2}{d^2}=\frac{k*3}{d+2}$$ <-----------------solve this.

kkrizka said:
Just try to look at it like a 1D problem. Along a line joining the two charges there will be a point where the sum of the fields is 0. Also using rules of repulsion/attraction for charges, you can figure out that the point will NOT be between the two charges. So the distance from one charge is d1, and the distance from the second charge is 2+d1.

Drawing a picture always helps. :)

how can it happen that it won't be between the charges?

https://www.physicsforums.com/latex_images/16/1629068-1.png [Broken]

why is it d+2.. ? where did the 2 come from?

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still need answer to this :( thanks to those who can help

rize said:
how can it happen that it won't be between the charges?
Just use your rules of repulsion/attraction between two charges. If the test change was placed between the two charges in the question, The negative would attract it left and the positive would push it away, towards the left. No matter how you add them, it would result in a vector pointing left.

rize said:
https://www.physicsforums.com/latex_images/16/1629068-1.png [Broken]

why is it d+2.. ? where did the 2 come from?

The 2 is the distance between the 2 charges. As I said earlier in my post, a diagram always helps, the red dot is the neutral point.
http://img87.imageshack.us/img87/2843/80141767hn2.th.png [Broken]

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## 1. Where is the neutral point located in an electrostatic field?

The neutral point in an electrostatic field is typically located at the center of the field, where the electric field strength is zero.

## 2. How is the neutral point determined in an electrostatic field?

The neutral point can be determined by finding the point where the sum of the electric field vectors from all charges in the field is equal to zero.

## 3. Is the neutral point always located in the same place in an electrostatic field?

No, the location of the neutral point in an electrostatic field can vary depending on the distribution and magnitude of charges in the field.

## 4. Can the neutral point be outside of the boundaries of an electrostatic field?

Yes, the neutral point can be located outside of the boundaries of an electrostatic field if there are charges present outside of the field that influence the electric field within it.

## 5. Why is the neutral point important in electrostatics?

The neutral point is important in electrostatics because it represents a point of equilibrium where the electric field strength is zero. This can have implications for the behavior of charged particles and the overall stability of the system.