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???