thank you for your answering, but i don't understand why the symmetry allows tot cancels out the effect of those charges.
at 10 .5 cm , the distance from one side of the charge of inner surface of the conductor is different from the opposite side. electric varies with the distance, doesn't...
For the configuration shown in the figure below, suppose a = 5.00 cm, b = 20.0 cm, and c = 25.0 cm. Furthermore, suppose the electric field at a point 10.5 cm from the center is measured to be 3.25 × 10^3 N/C radially inward and the electric field at a point 50.0 cm from the center is of...