在如图所示的各电场中，A、B两点电势相同的是（）

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问题选择题

答案

：A

：

题目分析：等势面上的各点电势都相等．

A、点电荷的等势面是以点电荷为圆心的同心圆，A对

B、在同一条电场线上沿电场线方向电势逐渐降低，B错

C、匀强电场的等势面是垂直于电场线的间距相等的平行线，A、B两点在不同等势面上，C错

D、等势面与电场线垂直，A、B两点在不同等势面上，D错

故选A

点评：在画等势面是一定要注意等势面与电场线垂直．

单项选择题

Looking back on my childhood, I am convinced (1) naturalists are born and not made. Although we were all brought (2) in the same way, my brothers and sisters soon gave up their pressed flowers and insects. (3) them, I had no ear (4) music and languages, I was not an early reader and I could not do mental arithmetic.Before World War I we (5) our summer holidays in Hungary. I have only the memory of the house we lived (6) , of my room and my toys. I can hardly (7) clearly the large family of grandparents, aunts, uncles and cousins who gathered (8) door. But I do have a clear memory of the dogs, the farm (9) , the local birds and, (10) all, the insects.I am a (11) , not a scientist. I have a p (12) of the natural world, and my enthusiasm has led me into varied investigation. I love discussing my favorite topics and enjoy (13) the midnight oil (14) reading about other people’s observations and discoveries. Then (15) happens that brings these observations together (16) my conscious mind. Suddenly you fancy (想象), you see the answer (17) the riddle, and books, of which some might honor with the title of scientific research.But curiosity, a keen eye, a good memory and enjoyment of the animal and plant world do not make a scientist; one of the outstanding and essential (18) required is self-discipline, a quality I lack. A scientist requires not only (19) but also hard training, determination and a goal. A scientist, up to a point, can be made. A naturalist is (20) . If you can combine the two, you get the best of both worlds.

第（13）空应选择（）

A．burning

B．making

C．hunting

D．turning

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填空题

______是贾德通过“水下打靶”实验总结出来的迁移理论。

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