Gauss's law on a charged sheet.

[pondzo]

Homework Statement

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

Homework Equations

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

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.

 

[Doc Al]

Your answer looks OK to me. What book are you using?

 

[Doc Al]

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.

 

[pondzo]

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

 

[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