Gauss Law

1. Apr 10, 2005

Rave Grrl

I used the formula (E * Area * cos(theta)) and got the wrong answer (.02529) and I really don't understand why. I need help

The square surface shown measures 4.0 mm on each side. It is immersed in a uniform electric field with magnitude E = 1930 N/C. The field lines make an angle of 35° with a normal to the surface, as shown. Take the normal to be "outward," as though the surface were one face of a box. Calculate the electric flux through the surface.

2. Apr 10, 2005

dextercioby

It looks correct (probably not the final #).U may have to check the units ($\left(1\mbox{mm})\right)^{2}=10^{-6} \mbox{m}^{2}$...

Daniel.

3. Apr 10, 2005

HallsofIvy

Staff Emeritus
35 degrees to the normal is 55 degrees to the surface. Did you try that?

4. Apr 10, 2005

dextercioby

Halls,she needs the scalar product between the electric field vector and the normal to the surface,which make an angle of 35° between them...

Daniel.

5. Apr 10, 2005

Rave Grrl

I tried 55, and it didn't work.

Is electrical flux supposed to be negative? Thats all I can think of. I don't know if that's right.

6. Apr 10, 2005

dextercioby

Depends on the sense of the electric field.If it enters the page or not.Your problem is pretty vague in this issue,because you haven't provided the drawing/picture.

Daniel.