# Finding electric field via potential

#### DannyPhysika

1. Homework Statement

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 c has to 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 via potential. What is the direction of the field

2. Homework Equations

V = k integral(0 to L) dq/r

E = -dV/dx

3. The Attempt at a Solution

Found everything except electric field. I've tried and gotten so confused as to how to implement it. I got this so far:

dV = kλdx/(d+x)

dV/dx = kλ/(d+x)

E = -k(c)(1m)/(2m) = -8.99 x 10^3 N/C

I know it's wrong but I'm so lost as to where to fix it. Thanks

Related Introductory Physics Homework Help News on Phys.org

#### DannyPhysika

I would like to know if either:

-3.47 x 10^3 N/C

or

-1.45 x 10^4 N/C

Are correct. Thank you :)

### Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving