• Support PF! Buy your school textbooks, materials and every day products Here!

Uniform electric field interaction

  • Thread starter kvanr
  • Start date
  • #1
7
0
1. Homework Statement
Electric charge is distributed along each side of a square. Two adjacent sides have positive charge +Q on each, two sides have -Q on each.

What are the x and y components of the net electric field at the center of the square? (Each side has length "a").


2. Homework Equations
E=F/q ?
F=k*q1*q2/r^2
k=9E9Nm^2/C^2

3. The Attempt at a Solution
Trying to come up with a differential equation? I don't know how to begin with having 4 sides.
 

Attachments

Answers and Replies

  • #2
marcusl
Science Advisor
Gold Member
2,684
353
You need the formula for the electric field from a charge (look in your book). Then argue from the special symmetry at the center of the square.
 
  • #3
7
0
You need the formula for the electric field from a charge (look in your book). Then argue from the special symmetry at the center of the square.
You mean the diagonal symmetry?

edit: Then that would make it equal 0 at the center?
I was thinking it was zero?
 
Last edited:
  • #4
marcusl
Science Advisor
Gold Member
2,684
353
Well, pick a side (say the top) and integrate the field at the center as you move the source point along (left to right). Mentally summing the vectors (look at the symmetry) will show you the net direction even without doing the math. Now that you know the answer for one side, it's straightforward to add the contributions of other three.

Hint: the field is not 0 at the center.
 

Related Threads for: Uniform electric field interaction

Replies
5
Views
2K
Replies
2
Views
7K
Replies
3
Views
6K
Replies
3
Views
5K
Replies
17
Views
15K
Replies
2
Views
9K
Replies
15
Views
6K
Replies
7
Views
977
Top