# Calculating Potential from electric field problem

1. Sep 20, 2008

### th3plan

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

An infinite, nonconducting sheet has a surface charge density σ = +8.77 pC/m2. (a) How much work is done by the electric field due to the sheet if a particle of charge q0 = 9.61 x 10-19 C is moved from the sheet to a point P at distance d = 2.45 cm from the sheet? (b) If the electric potential V is defined to be zero on the sheet, what is V at P?

Shouldnt the answer for part a be negative, because the solution manual says its positive,. I know V=-W$$_{}infty$$/q . Can someone explain me why this is so ?

2. Sep 20, 2008

### Redbelly98

Staff Emeritus
1. What's the direction of the force due to the electric sheet (i.e., away from or towards the sheet)?
2. In what direction does the charge move (towards or away from the sheet)?
The work done is positive if those two things are in the same direction, or negative if they're in opposite directions.

(b)
I don't understand your formula for V the way it is written.
How would you calculate V, given the electric field E?