試題詳解

50. A 5.0 nC point charge is embedded at the center of a nonconducting sphere (radius = 2.0 cm) which has a charge of -8.0 nC distributed uniformly throughout its volume. What is the magnitude of the electric field at a point that is 1.0 cm from the center of the sphere? (where electric constant k=9.0×10⁹ N·m ² /C² )
(A) 9.0 × 10⁴ N/C
(B) 1.8 × 10⁵ N/C
(C) 2.7 × 10⁵ N/C
(D) 3.6 × 10⁵ N/C
(E) 7.2× 10⁵ N/C