问题 问答题

图1-8是磁流体发电机工作原理图。

磁流体发电机由燃烧室(O)、发电通道(E)和偏转磁场(B)组成。在2500K以上的高温下,燃料与氧化剂在燃烧室混合、燃烧后,电离为正负离子(即等离子体),并以每秒几百米的高速喷入磁场,在洛仑兹力的作用下,正负离子分别向上、下极板偏转,两极板因聚积正负电荷而产生静电场。这时等离子体同时受到方向相反的洛仑兹力()与电场力(F)的作用,当F=时,离子匀速穿过磁场,两极板电势差达到最大值,即为电源的电动势。设两板间距为d,板间磁场的磁感强度为B,等离子体速度为,负载电阻为R,电源内阻不计,通道截面是边长为d的正方形,试求:

小题1:(1)磁流体发电机的电动势

小题2:(2)发电通道两端的压强差

答案

小题1:

小题2:

根据两板电势差最大值的条件

所以,磁流发电机的电动势为                        

设电源内阻不计,通道横截面边长等于的正方形,且入口处压强为,出口处的压强为;当开关S闭合后,发电机电功率为

根据能量的转化和守恒定律有

所以,通道两端压强差为

计算题
阅读理解

Arthur Miller (1915—2005) is universally recognized as one of the greatest dramatists of the 20th century. Miller's father had moved to the USA from Austria-Hungary, drawn like so many others by the “Great American Dream”. However, he experienced severe financial hardship when his family business was ruined in the Great Depression of the early 1930s.

  Miller's most famous play, Death of a Salesman, is a powerful attack on the American system, with its aggressive way of doing business and its insistence on money and social status as indicators of worth. In Willy Loman, the hero of the play, we see a man who has got into trouble with this system. Willy is “burnt out” and in the cruel world of business there is no room for sentiment: if he can't do the work, then he is no good to his employer, the Wagner Company, and he must go. Willy is painfully aware of this, and at a loss as to what to do with his lack of success. He refuses to face the fact that he has failed and kills himself in the end.

  When it was first staged in 1949, the play was greeted with enthusiastic reviews, and it won the Tony Award for Best Play, the New York Drama Critics' Circle Award, and the Pulitzer Prize for Drama. It was the first play to win all three of these major awards.

  Miller died of heart failure at his home in Roxbury, Connecticut, on the evening of February 10, 2005, the 56th anniversary of the first performance of Death of a Salesman on Broadway.

小题1:Why did Arthur Miller's father move to the USA?

A.He suffered from severe hunger in his home country.

B.He was attracted by the “Great American Dream.”

C.He hoped to make his son a dramatist.

D.His family business failed小题2:What can we learn about Willy Loman?

A.He treats his employer badly.

B.He runs the Wagner Company.

C.He is a victim of the American system.

D.He is regarded as a hero by his colleagues.小题3:After it was first staged, Death of a Salesman________.

A.achieved huge success

B.won the first Tony Award

C.was warmly welcomed by salesmen

D.was severely attacked by dramatists小题4:What is the text mainly about?

A.Arthur Miller and his family.

B.The awards Arthur Miller won.

C.The hardship Arthur Miller experienced.

D.Arthur Miller and his best-known play.