- #1
Romperstomper
Question: Three point charges, which are initially at infinity, are placed at the corners of an equilateral triangle with sides d. Two of the point charges have a charge of q. If zero net work is required to place the three charges at the corners of the triangle, what must the value be of the third charge?
What I did:
q = 2 of the charges
z = the third charge
d = the final distance between each charge
[tex] 0 = Uelec_q + Uelec_q + Uelec_z [/tex]
[tex] 0 = kq(\frac{-1}{d}) + kq(\frac{-1}{d}) + kz(\frac{-1}{d})[/tex]
[tex] 0 = \frac{-2kq}{d} - \frac{kz}{d} [/tex]
[tex] -2q = z [/tex]
The correct answer is [tex] \frac{-q}{2} = z [/tex]
Can anyone see what I did wrong? I've tried this problem a few times and have gotten the same answer each time.
What I did:
q = 2 of the charges
z = the third charge
d = the final distance between each charge
[tex] 0 = Uelec_q + Uelec_q + Uelec_z [/tex]
[tex] 0 = kq(\frac{-1}{d}) + kq(\frac{-1}{d}) + kz(\frac{-1}{d})[/tex]
[tex] 0 = \frac{-2kq}{d} - \frac{kz}{d} [/tex]
[tex] -2q = z [/tex]
The correct answer is [tex] \frac{-q}{2} = z [/tex]
Can anyone see what I did wrong? I've tried this problem a few times and have gotten the same answer each time.