31. A solid nonconducting sphere of radius R carries a charge Q distributed uniformly throughout its volume. At a certain distance r1 (r1 ＜ R) from the center of the sphere, the electric field has magnitude E. If the same charge Q were distributed uniformly throughout a sphere of radius 2R, the magnitude of the electric field at the same distance r1 from the center would be equal to
(A) E/8.
(B) E/2.
(C) 2E.
(D) 8E.
(E) E.

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統計： A(14), B(1), C(0), D(1), E(1) #2911329

詳解 (共 1 筆)

#5435531
V1 = (kQ / R2 )(r1/R) =kQr1/R3 = E , V2 = (kQ / (2R)2 )(r1/2R) = kQr1/8R3  = E/8 (A)
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