(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Consider 2 charges located in the x-y plane; q_{1}of magnitude 5 mC (millicoulombs) is located at the origin, and q_{2}of unknown magnitude is located at (x,y) = (0.1, 0) (in metres). The electric field E at position (0.03, 0.05) is found to be entirely in the +y direction (i.e. the x-component is zero). Determine the sign of charge q_{1}and the magnitude and sign of charge q_{2}.

2. Relevant equations

|q| = 5mC (microCoulombs)

F= qE ; q= charge, E= electric Field

E(r) = ƩE_{i}(r)

=1/(4*pi*ε_{°})*Ʃ(r-r_{i})*q_{i}/(r-r_{i})^{3}

3. The attempt at a solution

E_{1}(for one charge)= 1/(4*pi*ε_{°})*q_{1}/r^{2}

= 1/(4*pi*ε_{°})* (0.000005 C)/0.0015m

E= 2.996*10^{7}

Then I went and did,

E=1/(4*pi*ε_{°})[(q_{1}/r^{2})+q_{2}/(r-r_{2})^{2}]

rearrange for q_{2}and,

q_{2}= [E(4*pi*ε_{°})+(r^{2}/q_{1})](r-r_{2})^{2}

q_{2}= -29.9997 C. (This seems way to high to be correct)

So q_{1}is positive to make E in the + y direction.

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# Homework Help: 2 charges located in the x-y plane

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