Find an expression for the electrostatic energy of this charge distribution.

[warnexus]

Homework Statement

Homework Equations

work = kqqq/(distance)

The Attempt at a Solution

http://i33.photobucket.com/albums/d86/warnexus/electrodiag.jpg

 

[gneill]

Check the distance you've used for the diagonals. Substitute 'q' and 'q/2' for the appropriate charges and simplify.

 

[warnexus]

the distance I used for the diagonals is sqrt of a. I do not understand I do not have q/2.

 

[gneill]

the distance I used for the diagonals is sqrt of a. I do not understand I do not have q/2.

Is the length of a diagonal of a square of side length a equal to √a ?

You have two sizes of charge: One is 'q', the other is 'q/2'. Make the appropriate symbolic substitutions.

 

[warnexus]

Is the length of a diagonal of a square of side length a equal to √a ?

You have two sizes of charge: One is 'q', the other is 'q/2'. Make the appropriate symbolic substitutions.

oops the diagonal is suppose to be sqrt 2a^2.

heres the substitutions:

k(qq/a + qq/sqrt(2a^2) + qq/a -1/2qq/a -1/2qq/a -1/2qq/sqrt(2a^2))

 

[gneill]

Okay, but you can simplify further. For example, you can pull out the q² from each term.

 

[warnexus]

Okay, but you can simplify further. For example, you can pull out the q² from each term.

heres the simplification

kqq(1/a + 1/sqrt(2a^2) + 1/a - (1/a) - (1/2)/sqrt (2a^2)

 

[gneill]

You can collect the terms, putting them over a common denominator...