现代汽车变矩器的形式有三元件综合、四元件综合和五元件综合变矩器三种。（）
参考答案：错
小题1:Which of the following will help to improve your speech?
A．IELTS Listening .
B．Car and Driver.
C．Quick & Easy Meals.
D．Designing Effective Speech Interfaces.小题2:Who will probably be interested in Quick & Easy Meals?
A．Car fans.
B．English speakers.
C．Housewives.
D．Businessmen.小题3:How many of the four short passages are introductions of books?
A．One.
B．Two.
C．Three.
D．Four.
如图所示，一细导体杆弯成四个拐角均为直角的平面折线，其ab、cd段长度均为l1，bc段长度为l2．弯杆位于竖直平面内，Oa、dO′段由轴承支撑沿水平放置．整个弯杆置于匀强磁场中，磁场方向竖直向上，磁感应强度为B．今在导体杆中沿abcd通以大小为I的电流，此时导体杆受到的安培力对OO′轴的力矩大小等于______．
