题目

如图所示，绕在铁芯上的线圈、电源、滑动变阻器和电键组成闭合回路．在铁芯的右端套有一个表面绝缘的铜环A，下列各种情况中铜环A中没有感应电流的是（）     A． 线圈中通以恒定的电流     B． 通电时，使变阻器的滑片P作匀速滑动     C． 通电时，使变阻器的滑片P作加速滑动     D． 将电键突然断开的瞬间阅读理解（每题2分，共10分）My name is David Smith. I am a boy. I’m thirteen and I’m from England. I have a sister（妹妺）. Her name is Kate. She is eleven years old. I like playing basketball and football. I don’t like playing table tennis. There are twenty boys in my class. They like basketball and football, too.1.What’s the boy’s name?A. Tony B. Kate C. David Smith2.Where’s he from?A. English B. England C. China3.What’s his hobby(兴趣，爱好)?A. basketballB. footballC. basketball and football4.How old is he? .A .elevenB. thirteenC. twenty5.How many boys are there in the class?A. eleven B. thirteen C. twenty