PHY CAPACITOR

2007-03-22 3:46 am
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╙--------o 12V o ----- ╜

我想問上面個CAPACITOR會唔會CHARGE UP呀?
ASSUME INITIALLY UNCHARGED
同埋點解?

回答 (1)

2007-03-22 7:04 pm
✔ 最佳答案
如果我理解無錯的話就係只得一粒電芯connect with 一個capacitor, 個circuit 係無resistor or internal resistance?

如果真係咁的話呢, 咁個capacitor 就唔會charge up 啦. 因為我地睇charge up 或者係discharge, 好多時都會見一樣野 -- time constant == rc. time constant 就係代表住果一隻capacitor 要幾耐先至會fully charge up/ discharge. 但係今次呢, 因為 r=0, 所以係 ( t/rc )會變infinity, 所以無論幾耐都唔會charge up 到.

我地又可以從別一個方向去諗, 就係capacitor 的特性啦. capacitor 係一開通電的時候, 我地會當佢係無resistance 的電線, 係會short 左個circuit 架 (我諗呢樣你都知啦). 咁係一開始的時候, 咪好似只得一粒電芯自己用電線connect 住自己的正負兩極? 但係大家都知咁樣做個電芯係唔會lose energy 的, 咁即係話個capacitor 都唔會有任何energy 可以gain 到. 所以呢, 結論就係得capacitor 唔會charge up 到啦.

兩個method, 最緊要係明第一個, 第二個只係supplementary , okay?


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