# Ampere's Law and Infinite Current Sheets

1. Apr 7, 2012

### theBEAST

1. The problem statement, all variables and given/known data
Here is the question:
http://dl.dropbox.com/u/64325990/HW%20Pictures/infinite%20current%20sheet.PNG [Broken]

2. Relevant equations
∫B(dot)dl = μoIencl

3. The attempt at a solution
Here is my attempt:
http://dl.dropbox.com/u/64325990/HW%20Pictures/Photo%202012-04-06%2010%2045%2008%20PM.jpg [Broken]

According to the answer key my answer too large. The answer key has a coefficient of 1/2 in front of my answer... What did I do wrong? For my solution there is magnetic field in the sheet so the path is just L.

Last edited by a moderator: May 5, 2017
2. Apr 7, 2012

### tiny-tim

hi theBEAST!

hint: what does "enclosed" mean?

3. Apr 7, 2012

### theBEAST

OH so only half of the current is in that loop right?

Edit: Wait a second... What if my loop only enclosed 1/4 of the sheet so would my answer have a coefficient of 1/4 in front of it? Or would this not be legal as the amperian path is no longer symmetric?

4. Apr 7, 2012

### tiny-tim

no!

the current has to be in the loop, so you need the loop to be both above and below the current

(you're probably thinking of electric cases where one side of a gaussian loop goes through a conductor )