(2).電阻為R,長a寬b之四方迴路,以等速v,向右通過寬2b之均勻磁場B,則感應電流與時
間之變化:
a.在 0< t < b/v 時:
感應電流I = ε
/ R = avB / R (逆時)
b.在
b/v <,= t < 2b/v 時:
感應電動勢ε = 0
感應電流I = 0
c.在2b/v
<,= t < 3b/v 時:
感應電動勢ε = ΔøB
/ Δt = ΔA B / Δt = (a vΔt) B / Δt = avB
感應電流I = ε / R =
avB / R (順時)