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

题型:选择题

问题:

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

考点:变压器的结构和原理
题型:选择题

韭黄是我们冬季吃的蔬菜之一,它们呈黄色,这是因为在生产它们的过程中,菜农们没有给与

A.肥料

B.温度

C.水分

D.阳光

题型:选择题

证券市场可分为发行市场和交易市场,这反映了证券市场的( )。

A.管理结构

B.层次结构

C.交易场所结构

D.品种结构

题型:选择题

若x = -3是方程  x – a =" 6" 的解,则a =     

题型:选择题

Some time ago ,I discovered that one of my chairs had a broken leg. I didn’t think there would be any difficulty in getting it mended , as there are a whole lot of antique shops near my home. So I left home one morning carrying the chair with me. I went into the first shop expecting a friendly reception. I was quite wrong. The man wouldn't even look at my chair.

The second shop, though slightly more polite, was just the same, and the third and the fourth - so I decided that my approach must be wrong.

I went into the fifth shop with a plan in my mind. I placed the chair on the floor and said to the shopkeeper,“ Would you like to buy a chair?” He looked it over carefully and said, “ Yes, not a bad chair. How much do you want for it, sir?” “Twenty pounds,” I said. “OK, ”he said, “I’ll give you twenty pounds. ”“It ‘s got a slightly broken leg,” I said. “Yes, I saw that, it's nothing.”

Everything was going according to plan and I was getting excited. “What will you do with it?”I asked. “Oh, it will be easy to sell once the repair is done. ”“I'll buy it,” I said. “What do you mean? You’ve just sold it to me,” he said. “Yes, I know but I’ve changed my mind. I'm sorry, I'll give you twenty -seven pounds for it. ”“ Your must be crazy, ”he said. Then, suddenly the penny dropped. “I know what you want. You want me to repair your chair. ”“ You’re right, ”I said. “And what would you have done if I had walked in and said, Would you mend this chair for me?I wouldn't have agreed to do it,” he said. “We don’t do repairs, not enough money in it and too much trouble. But I’ll mend this for you, shall we say for a fiver?”He was a very nice man and was greatly amused by the whole thing.

小题1:We can learn from the text that in the first shop the writer ________.

A.was rather impolite  

B.was warmly received

C.asked the shopkeeper to repair his chair

D.asked the shopkeeper to buy his chair小题2:The expression “the penny dropped” in the last paragraph means the shopkeeper ________.

A.changed his mind       

B.accepted the offer

C.decided to help the writer    

D.saw the writer’s purpose小题3:How much did the writer pay?

A.£ 5.

B.£ 7.  

C.£ 20.

D.£ 27.小题4:From the text, we can learn that the writer was ________

A.honest

B.careful

C.funny

D.smart

题型:选择题

经常说的锅炉3大常规安全附件指()、()和()。

更多题库