- #1
Tina20
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Homework Statement
a) A -10.1 nC point charge and a +18.9 nC point charge are 13.8 cm apart on the x-axis. What is the electric potential at the point on the x-axis where the electric field is zero?
b) What is the magnitude of the electric field at the two points on the x-axis where the electric potential is zero? (Input your answers in order of increasing distance from the negative point charge
Homework Equations
E = kq/r^2
V=kq/r
where k=9x10^9
r is the radius
q is the charge
The Attempt at a Solution
a) So below is the equation I used but I am getting a negative number for r...someone please help, this is due by this Friday at midnight!
[kq1/(r+d)^2] + [kq2/r^2] = 0
[9x10^9 (-10.1x10-9)/(r + 0.138m)^2] + [9x10^9(18.9x10-9)/r^2] = 0
[-90.9/(r + 0.138m)^2] + [170.1/r^2] = 0
-90.9/(r + 0.138m)^2 = -170.1/r^2
-90.9/-170.1 = (r + 0.138m)^2 / r^2
0.53439 = (r + 0.138m)^2 / r^2
SQRT(0.53439) = (r + 0.138m)/r
0.731202 = r+0.138/r
0.73102r = r+0.138
0.73102r - r = 0.138
-0.268979r = 0.138
r = 0.138/-0.268979
r = -0.51305m
A distance can not be negative, so either my math is wrong or my process of equating the two is wrong. Some help would be greatly appreciated! Then hopefully I will be able to solve part b :)