16. A non-conducting sphere of radius R in the vacuum has a cavity of radius b at its center. The rest of the sphere has a uniform charge density p C/m³. What is the electric field at b < r < R?
(A)
(B)
(C)
(D)
(E) None of the above
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統計: 尚無統計資料
統計: 尚無統計資料