看板Physics
标 题Re: [求救]我是物理白痴, 请大家帮帮忙
发信站清华资讯(枫桥驿站) (Wed Sep 18 16:41:27 2002)
转信站Ptt!news.ntu!freebsd.ntu!news.cs.nthu!maple
※ 引述《[email protected] (Sushi)》之铭言：
> 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?
> 请高手指教, 谢谢
Cu原子量63.546
一个电子带电1.6E-19 C
19 uC要有 1.1875E14个带电电子被移除 (1.9E-5 / 1.6E-19)
3g Cu共有 3/63.546 * 6.02E23 = 2.842E22个原子
所以 1.1875E14/2.842E22 = 4.1784E-9
另一种算法 1 mole Cu 每一个原子拿掉一个电子
则会带电 6.02E23* 1.6E-19约等於96500库伦
96500*(3/63.546)=4555.75
则19E-6/4555.75=4.17E-9
应该是这样算 如有算错 请多见谅..
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