Calculating the electric flux

  • #1
8
2

Homework Statement


Hello,

A 3.60cm x 4.50cm rectangle lies in the xy-plane. What is the electric flux through the rectangle if E=(80.0i + 50k) N/C ?


Homework Equations



Φ = E * A =EAcos(θ)

The Attempt at a Solution



My attempt:

First convert the rectangle units from cm to m.

4.50cm = 0.045m
3.60cm = 0.036m

Find the area of the rectangle.

A = 0.036m x 0.045m = 0.00162 m^2

Find the magnitude of the electric field.

E = sqrt (50^2 + 80^2) = 94.34 N?C (aprox.)

Multiply the two,

electric flux = E * A = 0.15283 Nm^2 / C (aprox.)

However, this answer is wrong. Could anyone point me in the right direction? I am not sure how to incorporate the cosine into this. Thank you.
 

Answers and Replies

  • #2
Doc Al
Mentor
45,208
1,545
Your error is at the point where you multiply the two: that is a vector multiplication, not a magnitude multiplication.
 
  • #3
8
2
Thanks!
 

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