# Homework Help: Parallel Plates

1. Feb 4, 2007

### Soaring Crane

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

An infinite plane of charge with surface charge density sigma = 8.00 nC/m^2 lies in the yz plane at the origin, and a second infinite plane of charge with surface charge density sigma = -8.00 nC/m^2 lies in a plane parallel to the yz plane at x = 4.00 m. The electric field at x = 3.50 m is approximately

a.226 N/C
b.339 N/C
c.904 N/C
d.452 N/C
e.zero

2. Relevant equations

E = sigma/epsilon_0 for oppositely charged parallel plates

3. The attempt at a solution
E = sigma/epsilon_0 = (8.00*10^-9 C/m^2)/(8.85*10^-12) = 904 N/C ???

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

An infinite plane of charge with surface charge density sigma = 8.00 nC/m^2 lies in the yz plane at the origin, and a second infinite plane of charge with surface charge density sigma = -8.00 nC/m^2 lies in a plane parallel to the yz plane at x = 4.00 m. The electric field at x = 5.00 m is approximately

a.226 N/C
b.339 N/C
c.904 N/C
d.452 N/C
e.zero

2. Relevant equations

See below.

3. The attempt at a solution

If one draws a diagram for the E (and F) vectors, the vectors cancel each other out when outside the space between the plates, so it is 0?

Thanks.

2. Feb 4, 2007

### Staff: Mentor

It's all good. (I didn't check your arithmetic for the first one, but your method is correct.)