## Two small insulating spheres with radius

1. The problem statement, all variables and given/known data

Two small insulating spheres with radius 5.50×10−2 m are separated by a large center-to-center distance of 0.510 m. One sphere is negatively charged, with net charge -2.20 \mu C, and the other sphere is positively charged, with net charge 4.05 \mu C. The charge is uniformly distributed within the volume of each sphere.

Calculate E_1, the magnitude of the electric field at the midway point due to the sphere with charge -2.20 \mu C only.

2. Relevant equations

3. The attempt at a solution
I tried to use q/4pi(espolon not)r^2 but im not sure my radius is right because I have used half the distance for the distance and the radius of the sphere for the distance.
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 E(sphere) = Q/ 4pi(distance)^2 Notice that this the same as a point charge. You do not need to worry about the radius of the sphere for this part of the question.
 my problem was that I wasn't changing my units from micro coulombs to coulombs.