Electric Flux through Planar Surfaces

[exi]

Homework Statement

The drawing shows an edge-on view of two planar surfaces that intersect and are mutually perpendicular. Surface 1 has an area of 1.2 m², while surface 2 has an area of 3.5 m². The electric field E in the drawing is uniform and has a magnitude of 246 N/C.

Image:

http://img513.imageshack.us/img513/9947/physicspf4.jpg

What's the electric flux through surface 1? What about surface 2?

Homework Equations

$$\Phi = EAcos\Theta$$

The Attempt at a Solution

For #1, I attempted to do 246*1.2*cos(55°), which is incorrect at 169.3197 Nm²/C.

What exactly am I screwing up here?

 

[Dick]

If the field is perpendicular to the surface then flux is just EA. From this we conclude that the angle in your formula is the angle that the field makes with a normal to the surface, not the angle it makes with the surface.

 

[exi]

If the field is perpendicular to the surface then flux is just EA. From this we conclude that the angle in your formula is the angle that the field makes with a normal to the surface, not the angle it makes with the surface.

Yeah, I was thinking things through and got my angles a bit mixed in the process, as you can see.

Got it now - thanks.