- #1
mrcotton
- 120
- 0
Homework Statement
The diagram shows two charges, +4 μC and –16 μC, 120 mm apart. What is the distance from
the +4 μC charge to the point between the two charges where the resultant electric potential is
zero?
A 24mm
B 40mm
C 80mm
D 96mm
Homework Equations
potential equation
The Attempt at a Solution
Homework Statement
The correct answer is a 24mm
I get that we could simply use a 1:4 ratio and therefore r must be a fifth of the way from the 4 micro coulomb charge
However when I try and equate the formula and solve algebraicaly I seem to get the wrong answer if I put in the sign of the charges.
So my question is why do we just use the magnitude of the charges?