题型:选择题 . In order to learn the _______ of the family business, Bill took a job as messenger boy in one of the offices.A.ins and outsB.dos and don’tsC.heads and tailsD.p’s and q’s 查看答案
题型:问答题 如图所示,倾角为θ的光滑斜面上,有一长为L,质量为m的通电导线,导线中的电流为I,电流方向垂直纸面向外.现在图中加一个垂直斜面向下的匀强磁场,可使导线平衡,试求该磁场的磁感应强度是多少? 查看答案