Two point charges, Q1 = 2.9 μC and Q2 = 1.3 μC , are placed on the x axis. Suppose that Q2 is placed at the origin, and Q1 is placed at the coordinate x1 = − 4.0 cm (Figure 1). 
Part A Part complete At what point(s) along the x axis is the electric field zero? Determine the xcoordinate(s) of the point(s). Express your answer using two significant figures. If there is more than one answer, enter your answers in ascending order separated by commas.
SubmitPrevious Answers Completed Part B At what point(s) along the x axis is the potential zero? Determine the xcoordinate(s) of the point(s). Express your answer using two significant figures. If there is more than one answer, enter your answers in ascending order separated by commas.

a)
there is only one point on the axis where net electric field is zero
let us consider that point is at a distance d to the right of q2.
now, at that point electric field due to each charge must be same
k q1 / ( 4 + d) ^2 = k q2 / d^2
4/d + 1 = sqrt ( q1/ q2)
4/d + 1= sqrt ( 2.9/ 1.3)
d = 8.1 cm
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b)
there are two points where net potential considered to be zero
==>> between the charges
let us consider that the net potential is zero at a distance d to the left of q2
then
k q1 / (4  d) = k q2 / d
4/d  1 = 2.9 / 1.3
d = 1.238 cm
x co ordinate =  1.238 cm
====>> to the right of q2
k q1 / (4 + d) = k q2 / d
4/d + 1 = 2.9/ 1.3
d = 3.25 cm
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