Electric Flux of equilateral triangle

[msampsel]

Homework Statement

What is the flux of the uniform electric field E=8 N/C through an equilateral triangle with the side a=1m, if the normal vector makes 60 degrees to the direction of the electric field.

Homework Equations

$\phi$=EAcosø

The Attempt at a Solution

E=8 N/C
A= √3/4 m^2

Is the ø in this equation 60 degrees or 90-60 = 30 degrees?

 

[TSny]

Hello msampsel. Welcome to PF!

See if you can answer this question by considering a couple of special examples:

(1) What should the flux be if the angle between the normal and the field is 0? What value of ø in the formula will give this result?

(2) What should the flux be if the angle between the normal and the field is 90? What value of ø in the formula will give this result?

 

[msampsel]

(1) The flux would be the product of the field and the area (EA) because they are perpendicular to the plane. The value of ø would be 0 because cos(0)=1.

(2) The flux would be 0 because the field would then be parallel to the plane. The value of ø would be 90 because cos(90)=0.

 

[TSny]

OK, good. Based on those two examples, how is the angle ø in the formula related to the angle between the field and the normal direction?