问题 选择题
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=220sin100πt(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22V

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

答案:D

阅读理解

It was a cold winter afternoon before Christmas. My parents and I sat on the bench in Washington, D.C.’Union Station, waiting for the train. Inside the waiting hall were many people.

A boy sat nearby. His worn jacket, pale face, dirty hands all seemed to tell me that he was homeless.

“He must be cold and hungry. Maybe I should help him,” I said to myself.

Just at that moment, a well-dressed young couple walked towards him.

“Excuse me,” the man bent down. “My wife and I bought two meal boxes but one was enough for us. We hate to waste good food. Can you help us out and put this to use?” he handed the boy a meal box.

The boy thanked them and opened the box with joy and care. Suddenly he stopped. In the direction to which he looked, I saw an old man in rags-in a worn sweater, worn trousers and open shoes, entering the hall.

Putting the meal box aside, the boy stood and helped the old to his seat. He took off his jacket and covered it on the old man’s shoulders, saying, “A gentleman brought me this warm meal but I just finished eating. I hate to waste good food. Can you help me out?” He placed the still-warm meal box in the old man’s hands without waiting for an answer.

“Sure, son, but if only you share that sandwich with me. It’s too much for a man at my age. ”

We were all touched. Dad went away and soon returned with cups of hot chocolate and a big pizza. Mum and dad went up to those rags, “Excuse me…”

I rushed into a KFC and took out my pocket money. It was so cold that afternoon but I felt much warmer than I had ever thought possible.

小题1:Who gave the boy a meal box?

A.The young woman.

B.The old man.

C.The young man.

D.Mum and Dad.小题2:Why didn’t the boy have the meal?

A.He was not hungry.

B.He wanted to help the old man.

C.He didn’t like the food.

D.He saw a sandwich in the meal box.小题3:What did the writer most probably do at the end of the story?

A. He bought some food for the homeless.

B. He told his story to the people in the KFC.

C. He gave his pocket money to the homeless.

D. He asked the other passengers to help the homeless.

名词解释