问题 选择题

如图是两等量异种点电荷,以两电荷连线的中点O为圆心画出半圆,在半圆上有M、 P、 N三点,M、N两点在两电荷连线上,P点在两电荷连线的垂直平分线上,下列说法中正确的是(    )

A.M、 N两点的电场强度相同

B.M、N两点的电势相等

C.将正点电荷从M沿半圆运动到N电场力不做功

D.正点电荷在O点的电势能等于在P点的电势能

答案

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题目分析:根据等量异号点电荷电场线的对称性可知,M、N两处电场线疏密程度相同,则场强大小相同,场强方向都沿MN方向,所以M、N两点的电场强度相同,故A正确.根据顺着电场线方向电势降低可知,M点的电势高于N点的电势,故B错误.两等量异号点电荷连线的垂直平分线是一条等势线,P点的电势与O点电势相等,M点的电势高于N点的电势,故正电荷在O点的电势能等于在P点的电势能,将正电荷由M移到N电场力做正功,故C错误D正确.

单项选择题 A1/A2型题
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One day a mime(哑剧演员)is visiting the zoo and attempts to earn some money as a street performer. As soon as he starts to draw a crowd,a zookeeper drags him into his office.The zookeeper explains that the zoo's most popular attraction,a gorilla(大猩猩),has died suddenly and the keeper fears that attendance(出席人数) at the zoo will fall off.He offers the mime a job to dress up as the gorilla. The mime accepts.

The next morning the mime puts on the gorilla suit and enters the cage before the crowd comes.He soon discovers he can sleep all he wants,play and make fun of people and he draws bigger crowds than he ever did as a mime—the job he likes but loses.

However, with days going by,he begins to notice that the people are paying more attention to the lion in the cage next to his.Not wanting to lose the attention of his audience, he climbs to the top of his cage,crawls across a partition(隔墙),and dangles(悬挂)from the top to the lion’s cage. The lion gets angry at this. The scene is a fuel to the crowd.

At the end of the day he is given a raise for being such a good attraction—Well,this continues for some time.The crowds grow larger,and the mime’s pay keeps going up.

  Then one day when he is dangling over the lion he slips and falls.The mime is terrified. He starts screaming,  “Help me!”,but the lion is quick.The mime soon finds himself flat on his back looking up at the angry lion and the lion says, “Shut

up you fool! Do you want to get us both fired?”

小题1:The mime accepts the zookeeper’s offer because______________·

A.he has been out of work

B.he doesn’t like being a mime

C.he likes performing at the zoo

D.he is offered a higher pay there小题2:How does the mime find the job dressing up as the gorilla?

A.Hard and tiring.

B.Dangerous.

C.Easy and funny.

D.Boring.小题3:The mime’s first contact with the lion is to_________·

A.find pleasure for himself

B.get the lion’s attention

C.get his pay raised

D.win back his audience小题4:The underlined words “a fuel” in Paragraph 3 can be replaced by __________.

A. frightening    B common   C.exciting   D. familiar