- #1

JYangQi00

- 2

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## Homework Statement

My snipping tool is totally broken. So I'm going to leave a link :x

It's problem 1.6

http://ocw.mit.edu/courses/physics/8-02-electricity-and-magnetism-spring-2002/assignments/ps1a.pdf

## Homework Equations

[itex]E_{sheet}[/itex]=[itex]\frac{σ}{2ε_{0}}[/itex]

[itex]E_{slab}[/itex]=[itex]\frac{ρD}{2ε_{0}}[/itex]

[itex]\frac{Q}{ε_{0}}[/itex]=[itex]\oint[/itex]EdA

## The Attempt at a Solution

I got everything on the solutions page (http://ocw.mit.edu/courses/physics/8-02-electricity-and-magnetism-spring-2002/assignments/pss1.pdf) But I can't seem to understand why region I of Esheet is positive and Regions II and III are negative. If σ is a negative charge, shouldn't the signs be switched around?