Question

The distance between two charges q1 = -2.5 μC and q2 = 6.0 μC is equal to 1.0 m. Determine the point (other than infinity) at which the electric field is zero.

Answer 1

If we place the -2.5 charge at zero and 6.0 charge at 1 the E field will be zero somewhere (distance x) on the negative x axis.
so k q1/x(sqr) = k q2/(x+1)sqr or
q2/q1 = [(x+1)sqr]/x(sqr)= (x+1/x)sqr
so 2.4 = (x+1/x)sqr
1.55 = x+1/x = 1 + 1/x
.55 = 1/x
x = 1.82m