# The way of evaluating the electric field

1. Nov 25, 2008

### abcdefg10645

I upload the file which I described my problem thoroughly , I need someone who can help me to solve the problem.

Thanks!

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Last edited: Nov 25, 2008
2. Nov 25, 2008

### ZapperZ

Staff Emeritus
You want examples on how to use Gauss's Law?

Zz.

3. Nov 25, 2008

### Mårten

I think you will get more replies if you paste your question directly into your post in the forum - at least I don't like to open Word docs from sources I don't know. If you have pictures, you can upload them as attachments, and they will be shown directly in the post (if I recall correctly...).

4. Nov 25, 2008

### abcdefg10645

In fact , I need someone to display evaluating electric field by using the formula I wrote in the file .

Gausss law is quite convenient to reckon the electric field , but the method I mention is quite.......difficult to understand the meanings of R and$$\vec{}dS$$ .

And , I am sorry that I did not post the image but doc , for the image file is too "massive" to upload ....

Do not worry about that there exists virus .

I am sure that is thoroughly "pure"

5. Nov 25, 2008

### abcdefg10645

In fact , I need someone to display evaluating electric field by using the formula I wrote in the file .

Gausss law is quite convenient to reckon the electric field , but the method I mention is quite.......difficult to understand the meanings of R and$$\vec{}dS$$ .

6. Nov 25, 2008

### ZapperZ

Staff Emeritus
You removed the file?

As far as I can recall, the equation had an integral over a closed surface of a dot product of E and unit vector "n". This is exactly Gauss's law in the integral form, which should be nothing new to you if you are at the level of doing vector calculus form in your E&M class. That's why I had to double check if this is what you were asking.

Zz.

7. Nov 25, 2008

### clem

You have written Coulomb's law for the electric field. Examples of its use are in every elementary physics text.

8. Nov 25, 2008

### nasu

I think there is a mistake in your derivation. How does the the charge density (rho) go "inside" the del operator?
Del(rho/R) is not equal to rho*del(1/R). rho is a function of R. (If by rho you mean the charge density).
And also, in the last integral you have rho*dS... rho is a volume density. How do you integrate it over the surface? And from the point of view of physics, the field depends not only on the charge on the surface.. it cannot be right.

As they said above, use Gauss' law.