如图所示，在置于匀强磁场中的平行导轨上，横跨在两导轨间的导体杆PQ以速度v向右匀速移动，已知磁场的磁感强度为B、方向垂直于导轨平面(即纸面)向外，导轨间距为l，闭合电路acQPa中除电阻R外，其他部分的电阻忽略不计，则( )
A．电路中的感应电动势E=BIL
B．电路中的感应电流
C．通过电阻R的电流方向是由c向a
D．通过PQ杆中的电流方向是由Q向P
BC
题目分析：电路中的感应电动势E=BLV，A错。电路中的感应电流I=Blv/R，B对。跟据右手定则，磁感线穿掌心拇指指导体运动方向，则四指指高电势（Q点为高电势）通过电阻R的电流方向是由c向a，C对。通过PQ杆中的电流方向是由P向Q，D错
点评：难度较小，熟练掌握法拉第电磁感应定律的内容，明确电源为产生感应电动势的导体，在电源内部电流从负极流向正极
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| Most adults(成年人) once studied at school,had classes and did their homework every day.The same 1 is going on at school now. 2 it seems that doing weekend homework is 3 problem for the modern students. All the student should agree that weekend homework should be abolished (取消).It’s 4 for them studying at school five days a week.With homework to do on Saturday and Sunday,when can they find 5 to help around the house,go and see a game,or just have 6 at home? Because of these other activities(活动)，the homework can’t be finished until 7 so their homework is usually done in such a hurry that on Monday teachers are 8 and often threaten (威胁)to fail whole class of students because they know nothing about the 9 .If there were no weekend homework for the students to do ,they would be happy to go to school on Monday 10 having a good rest and to learn what the teachers teach. | |||
| ( )1. A. thing ( )2. A. Also ( )3. A. no ( )4. A. not enough ( )5. A. friends ( )6. A. a rest ( )7. A. Monday afternoon ( )8. A. pleased ( )9. A. lessons ( )10. A. until | B. school B. But B. another B. enough B. time B. an exam B. Saturday afternoon B. sorry B. games B. when | C. class C. Still C. one C. no good C. places C. a lesson C. Friday night C. unhappy C. interests C. before | D. homework D. Though D. other D. no use D. money D. a picnic D. Sunday night D. not worried D. activities D. after |