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问题 多选题

图甲所示的U-x图象表示三对平行金属板间电场的电势差与场强方向上的距离关系．如图乙所示，若三对金属板的负极板接地，图中x均表示到正极板的距离，则下述结论中正确的是（　　）

A．三对金属板两板电势差的关系为U1=U2=U3

B．三对金属板正极电势的关系φ1＞φ2＞φ3

C．三对金属板板间距离关系为d1＜d2＜d3

D．三对金属板板间场强大小是E1＞E2＞E3

答案

A、三对金属板的负极板接地，即电势为零．

根据电场的电势差与场强方向上的距离关系图象得三对金属板正极和负极电势差相等，所以三对金属板正极电势的大小相等，故A正确B错误．

C、根据电场的电势差与场强方向上的距离关系得U=-kx+b．即表示平行金属板间任意一点到负极的电势差与场强方向上的距离关系．

根据匀强电场中任意两点的电势差等于场强与这两点间沿着电场方向的距离的乘积，即U=Ed，

所以电场的电势差与场强方向上的距离关系图象斜率的绝对值大小等于场强大小，

所以三对金属板间场强大小有E1＞E2＞E3．d=

U
E
，板间距离关系为d1＜d2＜d3，故CD正确．

故选：ACD．

单项选择题

麻花钻将棱边转角处副后刀面磨出副后角主要用于（）。

A.铸铁

B.碳钢

C.合金钢

D.铜
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单项选择题

A recent poll indicated that half the teenagers in the United States believe that communication between them and their parents is (1) and further that one of the prime causes of this gap is (2) listening behavior. As a(an) (3) in point, one parent believed that her daughter had a severe (4) problem. She was so (5) that she took her to an audiologist to have her ear tested. The audiologist carefully tested both ears and reported back to the parent:"There’s nothing wrong with her hearing. She’s just (6) you out. "

A leading cause of the (7) divorce rate (more than half of all marriages end in divorce) is the failure of husbands and wives to (8) effectively. They don’t listen to each other. Neither person (9) to the actual message sent by the other.

In (10) fashion, political scientists report that a growing number of people believe that their elected and (11) officials are out of (12) with the constituents they are supposedly (13) Why Because they don’t believe that they listen to them. In fact, it seems that sometimes our politicians don’t even listen to themselves. The following is a true story: At a national (14) conference held in Albuquerque some years ago, then Senator Joseph Montoya was (15) a copy of a press release by a press aide shortly before he got up before the audience to (16) a speech. When he rose to speak, (17) the horror of the press aide and the (18) of his audience, Montoya began reading the press release, not his speech. He began, "For immediate release. Senator Joseph M. Montoya, Democrat of New Mexico, last night told the National... " Montoya read the entire six page release, (19) with the statement that he "was repeatedly (20) by applause.

4（）

A.audio

B.aural

C.hearing

D.listening
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