5Qs AL electrostatic

子路

2009-03-29 9:10 am

圖片參考：http://i256.photobucket.com/albums/hh182/zilu_photo/1f48c3c7.jpg

ANS : CACDC

Forthe first Q, I thought it's B. If they are of unlike charge, the routefrom A to B should point to the concentration of field line on theright hand side

For the 2nd Q, I thought it's D. I have no idea why it's A.

For the 3th Q, I simply used E=QV.

For the 4th Q, I thought the force should be 1N, by F=qE.

For the 5th Q, I got D. I am thinking whether the ans is wrong.

更新1:

for no.8 I don't understand that when there is net positive chage on X. The potential of X is zero. refer to the potential of a sphere: V=kQ/r

回答 (1)

天同

2009-03-30 1:39 am

✔ 最佳答案

7. No options are correct. You cannot tell any one of the given options is right without knowing the direction of the field lines.
8. At steady state, sphere Y is neutral and at earth potential. Sphere X has +ve induced charges and also at earth potential.
The reason is that both spheres are earthed, hence their potentials must be at zero (earth) potential.
Except the +ve induced charges on sphere X that are attracted by the -ve charge on the rod and hence cannot move, all other charges on the spheres would escape to earth.
9. You have got it right
10. Yes, it should be 1 N
11. Option D is the right answer. The +ve charge would fall to a lower potential, both electrically and gravitationally, after released.

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