electrostatics問題!!

2007-11-18 6:40 am

http://x90.xanga.com/b9ec314720533157972601/z118559049.bmp

A positively charged metal-coated ball X is repelled from the positively charged metal rod.When ball Y on an insulating handle is brought near the rod, X swings towards the rod as shown above.The ball Y could be
(1)an uncharge plastic ball
(2)an uncharged metal ball
(3)a negatively charged ball

answer is (2),(3)

點解o既????點解(1)唔得??????

更新1:

點解(3)同(2)又得呢?? 請各位高手幫手解答!!!!!!!thx~~~~~

更新2:

咁insulator係咪要rubbed or burn先會有charge???

回答 (1)

myisland8132

2007-11-18 7:18 am

✔ 最佳答案

(1) 錯
因為 plastic ball 的電荷不能自由運動﹐所以放個plastic ball 在旁邊不能對metal rod產生影響
(2)對
因為雖然個ball Y總體上不帶電﹐但因其上的電荷能自由運動﹐所以ball Y上的負電荷會趨向metal rod﹐結果metal rod上的正電荷會趨向ball Y﹐而負電荷會被排斥去ball X﹐因而ball X 會移向metal rod
(3)對
同(2)一樣﹐不過ball X 會移得更明顯

2007-11-17 23:20:04 補充：
應該這樣寫好些所以ball Y上的負電荷受metal rod上的正電荷吸引趨向metal rod﹐同時metal rod上的正電荷亦會趨向ball Y

2007-11-18 02:09:47 補充：
都可以這樣說將兩個絕緣體互相摩擦可以將電荷分離。( 其中一個帶正電,另一個帶負電)

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