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问题 选择题

如图所示，实线是电场中的等势线，为中心对称图形，部分等势线的上端标出了其电势数值；虚线是以中心点为圆心的圆，a、b、c、d是圆周跟等势线的交点；M、N是中轴线跟等势线的交点。下列说法正确的是

A．a、b、c、d四点的电势都相等

B．a、b、c、d四点的电场强度大小都相等、方向都相同

C．电子若从a点运动到c点，则克服电场力做的功大于0.4eV

D．电子若在M点由静止释放，则将沿中轴线穿越电场区域向N点运动，此过程加速度先减小、后增加

答案

答案：D

题目分析：由题意可知：，故选项A错误；由电场中等势面对称分布可知：，但由场强方向垂直于等势面可知其方向不相同，故选项B错误；电子从a点运动到c点，电场力做正功，故选项C错误；电子从M点释放后将沿直线运动，由等势面的疏密表示场强的强弱可知加速度先减小后增加，故选项D正确．

选择题

奥斯特发现了电流的磁效应，首次揭开了电与磁的联系；法拉第发现了电磁感应现象进一步揭示了电与磁的联系，开辟了人类的电气化时代。下列有关电磁现象的说法正确的是（   ）

A．导体在磁场中运动一定产生感应电流

B．电磁波在真空中无法传播

C．通电导体受到磁场的作用力与磁场方向无关

D．通电导体周围一定存在磁场
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A Recent Erymology of the Word "Culture"“文化”一词的新词源
Look in an old dictionary—say, a pre-1960 Webster’s—and you’ll likely find a definition of culture (1) looks something like this: "1．The cultivation of soil. 2．The raising, improvement, or development of some plant, animal (2) product. " This use of the word has its roots in the ancient Latin word cultura, "cultivation" or "tending," and (3) entrance into the English language had begun by the year 1430. By the time the Webster’s definition above was (4) , another definition had begun to take precedence over the old Latin denotation; culture was coming to mean "the training, (5) , and refinement of mind, tastes, and manners" (Oxford English Dictionary). The OED traces this definition, which today we associate (6) the phrase "high culture," back as far as 1805; by the middle of the 20th century, it was (7) becoming the word’s primary definition.
However, if you try a more modem source, like the American Heritage English Dictionary, (8) find a primary definition of culture which is substantially different than either of the two given above: "The totality (9) socially transmitted behavior patterns, arts, beliefs, institutions, and all other products of human work and thought. " Why such a (10) , and in such a (relatively) short period of time Well, in the past 40 years, the use of the (11) "culture" has been heavily influenced by the academic fields of sociology and cultural anthropology. These fields have gradually brought (12) was once a minor definition of culture (the last of eight definitions given in the old 1958 Webster’s quoted (13) ) into the mainstream.
It is easy to imagine how the US society which was so focused on "socially transmitted (14) patterns" in the sixties would come to need a word to describe the object of its interest. The civil (15) movement during this era brought everyone’s attention to bear on cultural differences within US society, while the Vietnam War (16) to emphasize the position of the US culture in relation to other world cultures.
Over time, these new uses (17) the word culture have eclipsed its older meanings, those associated with cultivation of the land and the production of (18) . You might say that an aspect of US culture over the past 40 years is its fascination with the (19) of culture itself—a fascination which has brought about many changes in the way we speak and the (20) of words which we commonly use.

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