A charge with a value of 3.0 x 10-5 C is located 2.5 cm from a charge with a value of 6.5 x 10-5 C. Determine the distance from the larger charge to the point where the total electric field is zero.

Answer 1

Let Q1 be the larger charge.
Let Q3 be the smaller charge.
Let Q2 be the charge at the point where the total electric field is zero.
Let x be the distance from the larger charge to this point.
(kQ1Q2)/x^2 = (kQ3Q2)/(0.025 - x)^2
Divide out common factors k and Q2:
Q1/x^2 = Q3/(0.025 - x)^2
Sub in Q1= 6.5 x 10-5 C and Q3 = 3.0 x 10-5 C and solve for x.