题目

王建同学对微风电风扇产生了兴趣，将它与小灯泡按如图甲所示的电路连接并进行实验．用手快速拨动风扇叶片，这时发现小灯泡发光，微风电风扇居然变成了机，此时它的工作原理是，电路可简化为乙图中的图． 答案：【1】发电【2】电磁感应【3】a--- Do you know that the meeting _______ this afternoon has been put _______ till next week? 　 --- No. Thanks for telling me. 　 A. to be held; off　　　 B. to be held; forward C. held; off　　 D. held; forward