※ 引述《SushiBar@kkcity.com.tw (Sushi)》之銘言：
> In copper, about one electron per atom is free to move about.
> A copper penny has a mass of 3 g.
> What percentage of the free charge would have
> to be removed to give the penny a charge of 19.0 uC?
> 請高手指教, 謝謝
Cu原子量63.546
一個電子帶電1.6E-19 C
19 uC要有 1.1875E14個帶電電子被移除 (1.9E-5 / 1.6E-19)
3g Cu共有 3/63.546 * 6.02E23 = 2.842E22個原子
所以 1.1875E14/2.842E22 = 4.1784E-9
另一種算法 1 mole Cu 每一個原子拿掉一個電子
則會帶電 6.02E23* 1.6E-19約等於96500庫倫
96500*(3/63.546)=4555.75
則19E-6/4555.75=4.17E-9
應該是這樣算 如有算錯 請多見諒..
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