[問題] 高中電磁感應問題
問題:一玻璃圓環水平放置於鉛直向上的磁場B中,
內有一直徑略小於環口的正電小球,
已知B(t)=Bo*ct,其中c為正的常數,
t=0時,小球的初速為逆時針的v,
則何者正確
Ans:小球將先減速為零,再反方向加速
想法:
可由法拉第定律可之
d(Bo*ct*piR^2)
ɛ=- -------------- = -Bo*c*pi*R^2
dt
ɛ=2piR*E=-Bo*c*pi*R^2
Bo*pi*R
E=- -----------
2pi
故知在玻璃環中有一個反向的電場,故會先減速再加速
問題:
用數學解釋沒有問題,但學生問為何在玻璃環中還會有電場產生,
可否有強者鄉民可以單純用正電荷+變化磁場,
用勞倫茲力F=qvB來解釋 這個正電荷的運動
謝謝
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