如图所示，理想变压器原、副线圈的匝数比为10：1，b是原线圈的中心接头，电压表V和电流表A均为理想电表．从某时刻开始在原线圈c、d两端加上交变电压，其瞬时值表达式为u=220 sin100πt（V）．下列说法正确的是（ ）A．当单刀双掷开关与a连接时，电压表的示数为22 B．当单刀双掷开关与b连接时，电压表的示数为11V C．当单刀双掷开关与a连接，滑动变阻器触头P向上移动的过程中，电压表的示数不变，电流表的示数变大 D．单刀掷开关由a扳向b时（滑动变阻器触头P不动），电压表和电流表的示数均变大  |
答案：D
| 完形填空。 | ||||
| "I can't believe what I'm hearing!" I thought to myself. Jeff was the last candidate (候选人) for president of Student Council. My best friend Tony came to me and said. "I'm sorry, Mike. I really thought you should be 1 ." Later that day, I happened to pass Jeff in the dining room. I offered him a 2 "Congratulations" and walked to my usual table. To my surprise, Jeff put his plate beside mine. "I'm, er-I'm just wondering if you would …consider coming to work on my team," he said 3 . "You are really smart, and you would be a great manager." "I don't think so," I replied, feeling unsure. "Well, if you change your mind, we are meeting tomorrow," he said before moving to another table. All that night, I thought about 4 from Jeff. Maybe being a part of the election process (选举过程) would give 5 a chance to make important changes at our school. I decided to join them. My first goal was to 6 a catchy advertisement. Within a few days, we designed a poster with Jeff's pictures showing him in a number of activities. No one could walk through any hallway 7 passing Jeff's smiling face. My next step was to 8 which new activities students would like to have at our school. Many of them wanted a chess club and a volleyball team. With the information I had collected, Jeff met with the headmaster. The headmaster 9 to add these activities to our school program. An eighth grader said, "It'll be 10 like attending a new school with Jeff as president." Hearing these words made my heart filled with 11 . I had wanted to become president of Student Council to make a difference. I achieved that and more by working as a member of Jeff's team. He became the most popular candidate and I was large part of his 12 . The fact that it has made a difference in other people's lives is the real prize. What a great feeling! | ||||
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V