[問題] 帶電荷圓環之電場值

[linbanden (冷板凳)]

Find the electric field a distance z above the center of a circular loop of

radius r which carries a uniform line charge λ

這一題在解答本上寫 ∫dl = 2

我知道積一圈起來當然是圓周長 2πr

可是想不透上下線是取多少? dl是多少?

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