如图所示,两根相距为l的平行直导轨ab、cd、b、d间连有一固定电阻R,导轨电阻

题型:选择题

问题:

如图所示,两根相距为l的平行直导轨ab、cd、b、d间连有一固定电阻R,导轨电阻可忽略不计;MN为放在ab和cd上的一导体杆,与ab垂直,其电阻也为R;整个装置处于匀强磁场中,磁感应强度的大小为B,磁场方向垂直于导轨所在平面(指向图中纸面内);现对MN施力使它沿导轨方向以速度v(如图)做匀速运动;令U表示MN两端电压的大小,则(  )

A.U=vBl,流过固定电阻R的感应电流由b到d

B.U=vBl,流过固定电阻R的感应电流由d到b

C.U=vBl,流过固定电阻R的感应电流由b到d

D.U=vBl,流过固定电阻R的感应电流由d到b

考点:右手定则导体切割磁感线时的感应电动势
题型:选择题

天癸的产生主要取决于()

A.肾中精气的充盈

B.脾气的健运

C.肾阳的蒸化

D.肝血的充足

E.肾阴的滋养

题型:选择题

民用建筑主体结构的耐用年限分为( )级。

A.二

B.三

C.四

D.五

题型:选择题

下列物质的用途中,与该物质的化学性质无关的是

A.酒精作燃料

B.CO作燃料

C.CO2作灭火剂

D.CaCO3细粉作牙膏原料

题型:选择题

旅游者心脏病猝发,导游人员应()。

A.让其就地平躺(头略高)

B.由患者亲属、领队或其他旅游者从患者口袋中寻找备用药物,让其服用

C.到附近的医院找医生前来救治

D.迅速送医院

E.按摩胸部

题型:选择题

阅读理解

     When you turn on the radio, you hear an advertisement. When you watch television, you hear and

see an advertisement. If you turn the pages of a newspaper or magazine, again you find an advertisement.

      If you walk down the street, you see one advertising board after another. All day, every day, people who want to sell you something compete to catch your attention. As a result, advertisements are almost

everywhere.?

     In the West, advertisements are the fuel that makes mass media work. Many TV stations, newspapers, magazines, radio stations are privately owned. The government does not give them money. So where does

the money come from? From advertisements. Without advertisements, there would not be these private

businesses.?

      Have you ever asked yourself what advertising is? Through the years, people have given different

answers to the question. For some time it was felt that advertising was a means of "keeping your name

before the public." And some people thought that advertising was "truth well told." Now more and more

people describe it in this way: Advertising is the paid, non-personal, and usually persuasive description of

goods, services and ideas by identified sponsors (明确的出资者) through various media.

      First, advertising is usually paid for. Various sponsors pay for the advertisements we see, read, and

hear over the various media. Second, advertising is non-personal. It is not face to face communication.

     Although you may feel that a message in a certain advertisement is aimed directly at you, in reality, it is

directed at large groups of people. Third, advertising is usually persuasive. Directly or indirectly it tells

people to do something. All advertisements try to make people believe that the product, idea, or service

advertised can do good to them. Fourth, the sponsor of the advertisement must be identified. From the

advertisement, we can see if the sponsor is a company, or an organization, or an individual. Fifth,

advertising reaches us through traditional and nontraditional mass media. Included in the traditional

media are newspapers, magazines, radio, television, and films. Nontraditional media include the mail,

matchbox covers, and billboards.?

1. The existence of the privately-owned mass media depends financially on _______.

A. the government   

B. advertisements?

C. their owners' families

D. the audience

2. According to the passage, who are most probably paying for the advertisements?

A. Companies.

B. Organizations.  

C. Individuals.

D. All of the above.?

3. Which of the following is considered nontraditional mass media?

A. Newspapers    

B. Magazines

C. The mail  

D. Films?

4. According to the passage, which of the following statements about the features of advertisements

    is NOT true??

A. The sponsors are always mentioned in the advertisements.

B. Advertising is meant for large groups of people.?

C. Advertising tells people to do something directly or indirectly.?

D. Advertising must be honest and amusing.?

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