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[問題] 2008 AL Physics MC -Electrostatics

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2008 AL Physics MC -Electrostatics

那道問題是:

一個接地的導體
擺近
一個帶負電的導體,

當然那個接地的導體會帶正電

但是我搞不懂 statement 3,

究竟那個帶負電的導體的電勢變得更正,變得更負,還是不變呢?
請指教

P.S.
我報考了2013的AL Physics
   

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我諗到啦,系咪咁呀?

[     -]    [+     ]

The left one is a -ve charged conductor.
The right one is an earthed conductor which becomes +ve
because of charging by induction.

The question asks about the change of the potential of the left conductor.

Recall:
(1) As the Electric Field inside a conductor is 0,
Potential is constant throughout the whole conductor.

(2) Electric potential of a point can be calculated by summing up k*dq/r

That is how to use the 2 points above:
Consider the potential of point A which is on the left bracket of the left conductor.
Because of the +ve charge on the right conductor,
V= k (+Q)/r_1 +  k (-Q)/r_2
obviously greater than the original potential.

Conclusion: More positive






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是不是Q13?
(1) true. obviously the sphere becomes +ve charged.
(2) false. 無啦啦charged conductor 點會lose +ve charge
(3) false. 這不用多想吧....有個+ve charge brought near 個conductor, 明顯potential 唔會變得more -ve la..

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引用:
原帖由 christinali 於 2012-11-14 04:04 PM 發表
是不是Q13?
(1) true. obviously the sphere becomes +ve charged.
(2) false. 無啦啦charged conductor 點會lose +ve charge
(3) false. 這不用多想吧....有個+ve charge brought near 個conductor, 明顯potent ...
我之前決定唔到如果左邊的導體的 charge 重新分布之後會唔會改變potential

經過數學表達之後,則好肯定potential提升

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