Homework Help: Electric Field of a finite line of charge

1. Sep 12, 2011

johnnyies

1. The problem statement, all variables and given/known data
I just took an exam and one of the questions gave us a finite line of charge and asked us to calculate the E-field at a point at a point P to the right of the line of charge.

here is a poor sketch

[+][+][+][+][+][+][+][+][+][+][+][+]---------------------------------- .P
(thin line of charge)

now my initial thought would be that E at point P = 0, since if we drew the field lines they would point radially outward and perpendicular to the line of charge. However, 0 was not any of the available answers.

The only equation given to us was the one for a point that is in the perpendicular bisector of the line of charge, which cannot apply in this case. How would we go about solving this?
2. Relevant equations

3. The attempt at a solution

2. Sep 12, 2011

Spinnor

You wrote,

"now my initial thought would be that E at point P = 0, since if we drew the field lines they would point radially outward and perpendicular to the line of charge. However, 0 was not any of the available."

I think that is true only for an infinite line of charge. I think you could divide the line of charge into small elements and add the electric field at point P due to all the elements of charge?