题目

均匀导线制成的正方形闭合线框abcd，线框的匝数为n、边长为L、总电阻为R、总质量为m，将其置于磁感应强度为B的水平匀强磁场上方某高度处，如图所示，释放线框，让线框由静止自由下落，线框平面保持与磁场垂直，cd边始终与水平的磁场边界平行，已知cd边刚进入磁场时，线框加速度大小恰好为，重力加速度为g，则线框cd边离磁场边界的高度h可能为 A.             B.               C.             D.用所给单词的适当形式填空。【1】I________（watch）TV every day.【2】I________（watch）TV with my grandma yesterday.【3】Many years ago, there _________（be）a small house.【4】We ________（live）in a small house ten years ago.【5】Thank you for_________（talk）to us.