Homework Help: Does This Answer Make Sense (basic EM)

1. Oct 8, 2011

ZenOne

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

The plastic rod of the length L=1 m has a non-uniform charge density λ=cx
where positive constant c =2x10-6 [some unit]. What unit does c have? Find the electric
potential at the point on the x axis 1 m to the left from the left end of the rod. Find the
electric field at that point as well, preferably via potential.

2. Relevant equations

V=k*integral(cdx)

3. The attempt at a solution

V=kc*integral(dx)-----V=kcx------V=17980V

Is it just me or is this completely wrong? This is not my solution--it's my teacher and I was under the impression that the integral would end up being (with d=end of rod to point P):

V=kc*integral(x/d+x)-----V=kc[L-d(ln)(1+L/d)]

He ttok his limits of integration as L to L+1, however, in the book it says it should be from 0 to L (even though that doesn't really affect the answer). It is his integration I do not agree with.

Thanks in advance for any clarification.

2. Oct 8, 2011

ehild

Last edited: Oct 8, 2011