試題詳解

12. Two infinite parallel surfaces carry uniform charge densities of 0.20 nC/m² and -0.60 nC/m². What is the magnitude of the electric field at a point between the two surfaces?
(A) 30 N/C,
(B) 5 N/C,
(C) 45 N/C,
(D) 10 N/C,
(E) 90 N/C.