# Electric field on a point charge

• skidkid
In summary, the problem involves finding the electric field produced by the nuclear charges at a certain point in an H2O molecule. The distance between the oxygen nucleus and each of the hydrogen nuclei is given, as well as the angle between the hydrogen atoms. The equation used to solve this problem is the law of cosines, but a drawing must be made first to determine the magnitude and components of the electric field vectors.
skidkid

## Homework Statement

The distance between the oxygen nucleus and each of the oxygen nuclei in an H2O molecule is 9.58*10^-11m; the angle between the H atoms is 105 degrees. Find the electric field produced by the nuclear charges (positive charges) at the point P at a distance of 1.20*10^-10m to the right of the oxygen nucleus.

## Homework Equations

The law of cosines.

## The Attempt at a Solution

I used the law of cosines to find the distance from the oxygen atom to the point P, but I don't know where to go from there.

skidkid said:

## Homework Statement

The distance between the oxygen nucleus and each of the HYDROGEN nuclei in an H2O molecule is 9.58*10^-11m; the angle between the H atoms is 105 degrees. Find the electric field produced by the nuclear charges (positive charges) at the point P at a distance of 1.20*10^-10m to the right of the oxygen nucleus.

## Homework Equations

The law of cosines.

## The Attempt at a Solution

I used the law of cosines to find the distance from the oxygen atom to the point P, but I don't know where to go from there.

Hi,

You have a mistake in your statement of the problem on the first line. I corrected it above for you. Here's the deal: you need to draw a picture of the situation first. Don't worry about equations until you have sketched your three nuclei and placed your point. Then at the point draw in a little vector arrow representing the electric field due to each charge. Hint: the vector for a given nucleus will point away from that nucleus. Now you are going to have to figure out the magnitude of that vector at the point. There's this nice equation that's got a q in the numerator and an r-squared in the denominator (also a constant out front) that gives you the magnitude of the electric field. Your job then is to figure out the components of each of the electric field vectors in the x and y directions and add them up (x components with x components and y components with y components). So you see the law of cosines is only part of it. I haven't see your drawing so I'm not sure where P is, but I'll bet that if you draw your picture with the x and y axes in the right place you can save yourself some work.

Hope this gets you started!

Last edited:

I would like to clarify that the electric field is not produced by the nuclear charges, but rather by the movement of electrons within the molecule. The nuclear charges only play a role in determining the overall charge of the molecule.

To find the electric field at point P, we first need to determine the charge distribution within the H2O molecule. This can be done by considering the electronegativity of the atoms involved and their relative positions within the molecule.

Once the charge distribution is known, we can use the Coulomb's law to calculate the electric field at point P. This law states that the electric field (E) at a point due to a point charge (Q) is given by E = kQ/r^2, where k is the Coulomb's constant and r is the distance between the point and the charge.

In this case, we will have to consider the electric fields produced by the oxygen nucleus and the two hydrogen nuclei separately, as they are located at different distances from point P. We can then use vector addition to determine the net electric field at point P.

It is also important to note that the angle between the H atoms (105 degrees) will affect the magnitude and direction of the electric field at point P. This can be taken into account by considering the components of the electric field in the x and y directions.

In summary, to find the electric field at point P, we need to consider the charge distribution within the H2O molecule, use Coulomb's law to calculate the electric fields produced by each charge separately, and then use vector addition to determine the net electric field at point P.

## 1. What is an electric field?

The electric field is a physical quantity that describes the strength and direction of the force that a charged particle experiences due to the presence of other charged particles. It is a vector field, meaning it has both magnitude and direction, and is typically measured in units of volts per meter (V/m).

## 2. What is a point charge?

A point charge is a hypothetical particle with a non-zero electrical charge that is concentrated at a single point in space. It is often used as a simplified model to describe the behavior of charged particles in electric fields.

## 3. How is the electric field on a point charge calculated?

The electric field on a point charge is calculated using Coulomb's Law, which states that the magnitude of the electric field at a given point is directly proportional to the magnitude of the charge and inversely proportional to the square of the distance between the two points. The equation for calculating electric field is E = kQ/r^2, where E is the electric field, k is the Coulomb's constant, Q is the charge of the point charge, and r is the distance from the point charge to the point where the electric field is being measured.

## 4. How does the electric field on a point charge vary with distance?

The electric field on a point charge follows an inverse square law, meaning that as the distance from the point charge increases, the electric field strength decreases. This relationship is described by the equation E = kQ/r^2, where r is the distance from the point charge. As r increases, the electric field decreases, but it never reaches zero as the field extends infinitely in all directions.

## 5. What is the direction of the electric field on a point charge?

The direction of the electric field on a point charge is always radial, meaning it points directly away from or towards the point charge depending on whether the charge is positive or negative. For a positive point charge, the electric field points away from the charge, while for a negative point charge, the electric field points towards the charge.

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