Three Charges Aligned on a Straight Wire

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The discussion focuses on determining the position of a charge -1.5q3 along a straight wire with two other charges, +q1 and -q2, such that the total electric field at the midpoint (P) vanishes. The charges are positioned at the origin and at a distance of 2L from the origin, respectively. The equation used to find the distance x is Etotal = 1/4πεo { E1 + E2 - E3 } = 0, where E1, E2, and E3 represent the electric fields due to each charge. The confusion arises from the notation of the charges and the expectation of multiple solutions for x.

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Three charges are aligned along a straight wire as show.
+C ?<--- -3/2 C --->? -C
+ q1 -3/2 q3 - q2
X----------------------------o-----------------------------X
P(midpoint)
|---------------------------- L-----------------------------2L
x=0 -----> +x

Assume that the +q1 charge is situated at the origin and the -q2 charge is located at distance 2L from the origin. Determine the distance that the -1.5q3 charge is from the origin in order that the total electric field at the midpoint of the wire vanishes.

Of course we have the positive charge (E field radially outward) and negative charge (E field radially inward) both directing in the +ve x direction. So we would expect to see the charge -3/2q3 to the left of P (-x) to cancel the two fields in the +x direction from q1 and q2. We would use Etotal = 1/4πεo { E1 + E2- E3 } = 0 and find the distance x by finding a root. Where E1= q/(0-L)2, E2= q/(2L-L)2, E3=3q/2(x-L)2.

I tried this one a few times just going in loops and don't want to confuse anyone one else. For some reason this question which is a trivial 1D problem is getting me lol. Thanks for your support.
 
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Also confused by your charge notation. Do you mean charge q1=-1.5q, etc?
 
You already have setup the equation correctly (if i understand correctly your three charges are q,-q and -1.5q).

What prevents you from solving the equation for x? You will find two solutions for x is that what confuses you?
 

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