# Electric field due to uniform charged line

1. Nov 17, 2013

### muaymike

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

Find the electric field at point p 5cm away from a 10cm line with a uniform charge of 2x10^-4C.
so its uniformly charged from 0 - 10cm and then point p is at 15cm

This question is broken down into 4 step by step parts:

first is to consider 100 individual charges equally spaced apart and determine what the charge of each would be to get a total of 2x10^-4C

Next one asks what is the distance from the first charge to our point p, and distance from last charge to point p

The third one is where I'm stuck, it asks what is the distance between the neighboring charges. write an expression for distance rn from the nth charge to point p.

2. Relevant equations

3. The attempt at a solution

For the first part, the charges would have 2/100 x 10^-4 C each. The second part, the distance from the first to point p is 15cm and from the last to p is 5cm. The third part, I can't find a way to express this distance. I believe it should have a dr but it could be just 15-xn. I am really drawing a blank right now
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Nov 17, 2013

### Staff: Mentor

If you label the first one with n=1 and the last one with n=100, you need a function f(n) such that f(1)=5cm and f(100)=15cm.
As the distance between all points is the same, this function is linear...

(a different, easier problem: what would you with just three points, if the first point is at 5cm and the third point at 15cm?)