At what points is the potential zero?

[Kali8972]

I was wondering if someone could help get me started on this problem. I thought I knew how to solve it but keep coming up with the wrong answer:

A 2.9 µC is at x = 0 and a -2.0 µC charge is at x = 3.5 cm. (Let V = 0 at r = .)

(a) At what point along the line joining them is the electric field zero?
x = cm
(b) At what points is the potential zero?
x = cm (smaller x value)
x = cm (larger x value)


a) [(2.9e-6 C)k]/(.055+ x)^2 = [k(2e-6)]/(x^2)

k's cancel.. and then use quadratic to find it but the values aren't the right ones... What am I missing?

Any help would be appreciated!
Thanks!

 

[quantumdude]

a) [(2.9e-6 C)k]/(.055+ x)^2 = [k(2e-6)]/(x^2)

Your problem is that you've got the $2.9\mu C$ charge sitting at x=-0.55cm, and you've got the $-2\mu C$ charge sitting at the origin.

(edited for typos)

 

[Kali8972]

well yeah I guess that would make things a little more difficult! haha thanks!