Electrostatics Line Charge question

1. Feb 3, 2017

grandpa2390

1. The problem statement, all variables and given/known data
Find the Electric field a distance z above one end of a straight line segment of length L that carries a uniform line charge λ

2. Relevant equations
Complicated formula due to lack of font for the notation used by the author of the book. so I wrote it out. I did my best to differentiate between the script r and pi.

just in case I did a terrible job, only the first "r" is pi, the rest are script r's

3. The attempt at a solution

My professor says during the lecture while doing this problem that the λ is not dependent on r so is a constant and can be pulled out of the integral, but then it also just disappears from the problem completely.

Why?

2. Feb 3, 2017

cnh1995

Your working is hard to read. It would be better if you typed the equations. You can use LaTeX.
https://www.physicsforums.com/help/latexhelp/
It shouldn't.
You need to first find the horizontal and vertical components of the field separately.

3. Feb 3, 2017

haruspex

Did your professor say that, or is it something you observe? It is still there in your final equation.

4. Feb 3, 2017

Diegor

Inside your integral there is a vector and it's magnitude is not 1 (as one can see in the drawing) so this magnitude will be there multiplying the argument and that is not right. You should be carefull when solving the integral.

Sorry i didn't see the hat over the u. That indicates that it is a unity vector.

5. Feb 4, 2017

grandpa2390

nvm
I got it.

Last edited: Feb 4, 2017
6. Feb 4, 2017

sry