8. A thin circular disk of radius R carries a total charge Q uniformly distributed on its surface. Assuming symmetric electric field on the two sides of the disk, which of the following expressions is a good approximation of the electric feld strength at a distance r above the center of the disk, where r << R?
(A) 
(B) 
(C)
(D)
(E)
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統計: A(0), B(0), C(0), D(2), E(1) #2740286
統計: A(0), B(0), C(0), D(2), E(1) #2740286
詳解 (共 1 筆)
#7430254
所以這題如果看到r遠小於等於R
就必須立馬想到要視為無限大帶電平板

而c選項指的是點電荷的電場公式
適用於r遠大於R
可以由庫倫定律的k常數推得
ㅤㅤ
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