# Need help with Proper integral of a uniformly charged rod

1. Sep 13, 2009

### db2dz

1. The problem statement, all variables and given/known data

A uniformly charged rod is places along the x-axis from x=0 to x= L. carefully set up, but do not solve the proper integral to determine the x component of the electric field at the point (L,a)

2. Relevant equations
E=u$$\int \frac{dq}{(r^2)}$$

for a line dq=λdl

3. The attempt at a solution
i know for a line dq=λdl
i think its something along the lines of
Ey=Kλy=$$\int \frac{dx}{(x^2y^2)^(3/2)}$$ from 0 to L

I have no idea if this is right. I am using my notes to guide me.

2. Sep 13, 2009

### gabbagabbahey

Coulomb's law for a linear charge distribution is:

$$\textbf{E}(\textbf{r})=\frac{1}{4\pi\epsilon_0}\int \lambda(\textbf{r}')\frac{\textbf{r}-\textbf{r}'}{|\textbf{r}-\textbf{r}'|^3}dl'$$

Where $dl'$ is an infinitesimal length of the source, located at $\textbf{r}'$, and the integration is over the entire line of charge.

Use $\textbf{r}=x\mathbf{\hat{x}}+y\mathbf{\hat{y}}+z\mathbf{\hat{z}}$ and $\textbf{r}'=x'\mathbf{\hat{x}}+y'\mathbf{\hat{y}}+z'\mathbf{\hat{z}}$ to find the x-component.