题型:选择题 矩形线圈在匀强磁场中匀速转动,磁通量的变化如图所示,则下列说法正确的是( )A.t2、t4时刻线圈通过中性面B.t2、t4时刻线圈中电动势最大C.从t1时刻到t3时刻的过程中电动势方向不变 D.磁通量变化周期、电动势变化周期、线圈转动周期相同 查看答案
题型:选择题 Sir, you _______ be sitting in this waiting room. It's for women and children only. [ ]A. oughtn't to B. can't C. won't D. needn't 查看答案