如图所示，理想变压器的原副线圈匝数比n1：n2=1：10，副线圈与阻_爱下问搜题

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如图所示，理想变压器的原副线圈匝数比n₁：n₂=1：10，副线圈与阻值R=20Ω的电阻相连．原线圈两端所加的电压u=20

sin20πt(V)，则（　　）

A．副线圈输出交流电的频率为10Hz

B．交流电压表的示数为20V

C．电阻R上消耗的电功率为2kW

D．原线圈中电流的最大值为100A

答案

AC

完形填空

I'd been travelling for long hours on a lonely country road when I had a flat tire. So I had to stop and get the tools to       the problem. It certainly wasn’t       doing this with a white shirt and suit on.
Nightfall was approaching. Suddenly a car pulled       from behind me. A man got out and offered to         me. Seeing his unpleasant appearance and tattoos(纹身)on his arm, I became        as thoughts of robberies flashed through my mind. But       I could say anything he had already begun to take the tools to change the       . While watching him I happened to look back at his car and noticed someone sitting in the passenger seat. This had        me.
Then, without       , it began to rain. He suggested that I wait in his car because my car was unsafe. As the rain increased, getting us wet within seconds, I        agreed. When I settle into the back seat, a woman’s voice came from the front seat. “Are you all right?” She turned around to me. “Yes, I am.’’ I replied with much        when seeing an old woman there. It must be his Mom, I thought. To my      , the old woman was a neighbor of the man who was helping me. “Jeff insisted on stopping when he saw you      with the tire. ”“I am grateful for his help, ” I said. “Me, too!” she said with a smile. He helped drive her to see her husband twice a week in a nursing home. She also said that he       at the church and tutored disadvantaged students.
The rain stopped and Jeff and I changed the tire. I tried to offer him money and of course he     it. It was shameful that I judged people by the way they       . As we shook hands I began to apologize for my     . He said, ‘‘I experience that same        often. People who look like me don’t do nice things. I        thought about changing the way. But then I saw this as a chance to make a       . So I’ll leave you with the same question I ask everyone who takes time to know me. If Jesus returned tomorrow and walked among us again, would you recognize Him by what He wore or by what He did?’’

B． disappointed

C． frightened

D． discouraged

C． expression

B． embarrassed

C． discouraged

C． unwillingly

C． satisfaction

D． excitement

A．volunteered

A．selfishness

单项选择题

如图所示电路的戴维南等效模型为（）。

A.A

B.B

C.C

D.D