问题 选择题

图为静电除尘机理的示意图,尘埃在电场申通过某种机制带电,在电场力的作用下向集尘极迁移并沉积,以达到除尘目的,下列表述正确的是(   )

A.到达集尘极的尘埃带正电荷.

B.电场方向由集尘极指向放电极.

C.带电尘埃所受电场力的方向与电场方向相同.

D.同一位置带电荷量越多的尘埃所受电场力越大.

答案

BD

场强方向由正极到负极,即由集尘极到放电极,尘埃向集尘极运动即说明所受电场力跟场强方向相反则尘埃带负电,根据F=Eq可知)同一位置带电荷量越多的尘埃所受电场力越大,BD正确。

连线题
阅读理解

阅读理解

     It is hardly surprising that clothing manufacturers (生产商)follow certain uniform standards for various

features(特征)of clothes.What seems strange,however,is that the standard adopted for women is the

opposite of the one for men.Take a look at the way your clothes button.Men's clothes tend to button

from the right, and women's from the left.Considering most of the world's population-men and women-are

righthanded,the men's standard would appear to make more sense for women.So why do women's clothes

button from the left?

      History really seems to matter here.Buttons first appeared only on the clothes of the rich in the 17th

entury, when rich women were dressed by servants.For the mostly righthanded servants,having women's

shirts button from the  left would be easier.On the other hand, having men's shirts button from the right

made sense, too.Most men dressed themselves,and a sword drawn from the left with the right hand would

be less likely to get caught in the shirt.

      Today women are seldom dressed by servants,but buttoning from the left is still the standard for them.

Is it interesting? Actually, a standard, once set, resists change.At a time when all women's shirts buttoned

from the left,it would have been risky for any single manufacturer to offer women's shirts that buttoned

from the right.After all, women had grown so used to shirts which buttoned from the left and would have

to develop new habits and skills to switch.Besides, some women might have found it socially awkward to

appear in public wearing shirts that buttoned from the right,since anyone who noticed that would believe

they were wearing men's shirts.

1.What is surprising about the standard of the clothing industry?

A.It has been followed by the industry for over 400 years.

B.It is different for men's clothing and women's.

C.It works better with men than with women.

D.It fails to consider righthanded people.

2.What do we know about the rich men in the 17th century?

A.They tended to wear clothes without buttons.

B.They were interested in historical matters.

C.They were mostly dressed by servants.

D.They drew their swords from the left.

3.Women's clothes still button from the left today because____.    

A.adopting men's style is improper for women

B.manufacturers should follow standards

C.modern women dress themselves

D.customs are hard to change

4.The passage is mainly developed by________.

A.analyzing causes

B.making comparisons

C.examining differences

D.following the time order