阿摩線上測驗
50. Charges are distributed non-uniformly in between the space of two infinitely long concentric cylinders of radius R and 2R,respectively, as shown in the figure on the right. There is no charge in the region r < R and r > 2R. In the region R<r<2R， 
(A) The electric field in the region R < r < 2R decays with r.
(B) The electric potential in the region R <r < 2R decays linearly with r.
(C) There is a positive surface charge residing on the inner surface of the outer cylinder.
(D) The electric potential in the cavity region is 0.
(E) None of the above.
統計： A(0), B(0), C(1), D(2), E(3) #3239598
