如图所示，一理想变压器原线圈匝数为n1，副线圈匝数为n2，原线圈所接电源为交变电流，副线圈上接有一电阻R，原、副线圈所接电表均为理想电表．若只增加副线圈的匝数n2，则（ ）
A．交流电的频率变大
B．电流表A1的示数变小
C．电流表A2的示数变大
D．电压表v的示数变大
A、若只增加副线圈的匝数n2，交流电的频率不变，故A错误；
B、若只增加副线圈的匝数n2，原副线圈电压与匝数成正比，所以副线圈电压U2增大，电压表v的示数变大．
根据I=
得电流表A2的示数变大，U R
根据P=UI得副线圈输出功率增大，所以理想变压器的输入功率增大，
原副线圈的电压不变，所以电流表A1的示数变大，故B错误，CD正确；
故选：CD．
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| Several pieces of advice I've gotten in my life have really made a difference. "Be 1 to people." This sounds quite common, but I'll never 2 my father telling me that. I was ten, and I had been rude to someone. He said, "There is no 3 in being rude to anyone at any time. You never know who you're going to meet later in life. 4 .you don't change anything by being rude. 5 you don't get anywhere." " 6 that you can do anything you want to do. Don't let anyone say, 'You're not 7 enough…it's too hard…it's a bad 8 …no one has done that before…girls don't do that. '"My mom gave me that advice in 1973. And it 9 me to never worry about what others were saying about my 10 direction. "Always do the 11 job you can do at whatever you're assigned, even if you think it's 12 ." Jerry Parkinson, an assistant advertising manager and my boss at P&G, told me this in 1979.Here I had just 13 from Harvard Business School(HBS), and I was assigned to determine 14 the hole in the Ivory shampoo bottle should be: 3/8 of an inch or 1/8 of an inch. I did research, focus groups...and I would come home at night 15 how I had gone from HBS to this. But later I realized that any job you're given is a(n) 16 to prove yourself. "Don't be a credit hog (吝惜赞扬的人). If you're 17 in the neighborhood of good things, good things will 18 to you." Tom Tierney, who was my boss at Bain in 1981 and is now on the eBay board, told me this. It's 19 ? you get ahead by crediting (赞扬) other people. Finally, in 1998, I was in New York 20 the big celebration as eBay went public (上市). My husband is a doctor. I called into his operating room and told him the great news. And he said, "That's nice." | |||||
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