问题 选择题

如图11所示,有两根长为L、质量为m的细导体棒a、b,a被水平放置在倾角为45°的光滑斜面上,b被水平固定在与a在同一水平面的另一位置,且a、b平行,它们之间的距离为x.当两细棒中均通以电流大小为I的同向电流时,a恰能在斜面上保持静止,则下列关于b的电流在a处产生的磁场的磁感应强度的说法正确的是          (  )

A.方向向上

B.大小为

C.要使a仍能保持静止,而减小b在a处的磁感应强度,可使b上移

D.若使b下移,a将不能保持静止

答案

答案:B

由安培定则可知b的电流在a处产生的磁场的磁感应强度方向向上,A错误.a的受力如图甲所示.

tan45°=,所以B=,B错.b无论上移还是下移,b在a处的磁感应强度均减小.若上移,a的受力如图乙所示.上移过程中FN逐渐减小,F先减小后增大,故C正确.若使b下移,同理可分析a将不能保持静止,D正确.

选择题
阅读理解

If you exhibit positive characteristics such as honesty and helpfulness, the chances are that you will be thought as a good-looking person, for a new study has found that the perception (认知) of physical attractiveness is influenced by a person's personality.

The study, which was led by Gary W.Lewandowski, has found that people who exhibit negative characteristics, such as unfairness and rudeness, appear to be less physically attractive to observers.In the study, the participants viewed photographs of opposite-sex individuals and rated them for attractiveness before and after being provided with information about their personalities.

After personality information was received, participants also rated the probability of each individual' s becoming a friend and a dating partner.Information on personality was found to significantly change the probability, showing that cognitive (认知的) processes modify (修改) judgments of attractiveness.

"Thinking a person as having a desirable personality makes the person more suitable in general as a close relationship partner of any kind," said Lewandowski.

The findings show that a positive personality leads to greater expectation of becoming friends, which leads to greater expectation of becoming romantic partners and, finally, to being viewed as more physically attractive.The findings remained consistent regardless of how "attractive" the individual was formerly thought to be or of the participants' current relationship status.

"This research provides a positive outcome by reminding people that personality goes a long way toward determining your attractiveness; it can even change people's impressions of how good-looking you are," said Lewandowski.

小题1:In the study the participants were required to _____.

A.try to make friends with each other

B.try to prove positive characters make people more attractive

C.exhibit negative characters such as unfairness and rudeness

D.rate one's attractiveness by photos before and after knowing her or his personality小题2:What's the CORRECT order of how cognitive processes modify judgments of attractiveness?

a.find a person with a positive personality

b.view the person more physically attractive

c.want to make friends with the person

d.want to be his/ her romantic partner

A.a→c→d→b

B.d→c→b→a

C.c→b→a→d

D.a→d→c→b小题3:Which of the following is WRONG according to the passage?

A.The research reminds people to pay more attention to the personality.

B.Personality can change people's impressions of one's appearance.

C.The judgment of one's attractiveness always stays unchanged.

D.Positive personality may lead to more friends.小题4:The passage is written in a(n) _____ tone.

A.subjective

B.objective

C.sceptical

D.negative小题5:Who are the intended readers of this passage?

A.People with positive characteristics.

B.Good-looking people.

C.People with negative characteristics.

D.General people.