# Relation between Electric Potential and Electric Field

1. Sep 17, 2015

### Alan I

1. The problem statement, all variables and given/known data
In a certain region of space, the electric field along the x-axis is given by:

E = 1.2x - 3.06, where E is in N/C and x is in meters.

If you set the electric potential equal to zero at (4.39 m,0), find the electric potential, in V, at the point (7.22 m,0).

2. Relevant equations
V = - ∫E * dl

3. The attempt at a solution

V = - ∫ (1.2X-3.06) dx

⇒ V = - [1.2X2/2 - 3.06X]02.83

⇒V=3.85 → which is http://www.dabur.com/odomos/images/wrong_sign.jpg [Broken] ...any suggestions?

Last edited by a moderator: May 7, 2017
2. Sep 17, 2015

### Orodruin

Staff Emeritus
You have the wrong integration boundaries and you are missing the term due to the potential at x = 4.39 m.

3. Sep 17, 2015

### rude man

First, find the potential difference between the two points.
Then set the one to zero & get the other.

4. Sep 17, 2015

### Alan I

potential difference between the two points: Vba = - ∫4.397.22 (1.2X-3.06) dx

⇒ Vba = -[1.2X2/2-3.06X]4.397.22
= -(9.184+1.870)
= -11.054
⇒-11.054 = Vb - Va

Va=0

⇒Vb = -11.054 V

does that make more sense?

5. Sep 17, 2015

### rude man

A whole lot more!

P.S. I didn't check the math.