# Gauss's law on a charged sheet.

1. Apr 22, 2014

### pondzo

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

find the field produced by a uniformly charged sheet carrying 87 pC/m2

2. Relevant equations

$\oint \vec{E}.d\vec{A}$ = qenclosed/$\epsilon$

3. The attempt at a solution

$\Phi$= $\sigma$A/$\epsilon$
$\Phi$=$\oint E.dA$ = $E(2A)$

2EA= $\sigma$A/$\epsilon$
E = $\sigma$/(2$\epsilon$) = 4.92 N/C where I use 8.85*10-12 for $\epsilon$ (this has been the value used through the book)
However the book says the answer is 49 kN/C
could someone point out my error? Thanks.

2. Apr 22, 2014

### Staff: Mentor

3. Apr 22, 2014

### Staff: Mentor

Since you are off (from the book's answer) by 104, I wonder if the charge density was meant to be in pC/cm2, not pC/m2.

4. Apr 22, 2014

### pondzo

I'm using Richard Wolfson's: essential university physics 2nd edition, ch 21 qn 33.

5. Apr 22, 2014

### pondzo

yeah that might be the problem, as i have seen similar qns to this one online but they use pC/cm^2 instead of pC/m^2