题干

关于电阻和电阻率的说法中,正确的是             (    )

A:导体对电流的阻碍作用叫导体的电阻,因此只有导体中有电流通过时才有电阻

B:金属导体的电阻率与导体长度成正比,与横截面积成反比

C:某些金属、合金和化合物的电阻率随温度的降低会突然减小为零,这种现象叫做超导现象。发生超导现象时的温度叫”转变温度”

D:将一根导线等分为二,则半根导线的电阻和电阻率都是原来的二分之一

上一题 下一题 0.0难度 选择题 更新时间:2019-01-10 05:04:24

答案(点此获取答案解析)

A

同类题4

写作

    There are two factors which determine an individual's intelligence. The first is sort of brain he is born with. Human brains differ considerably, some being more capable than others. But no matter how good a brain he has to begin with, an individual will have a low intelligence unless he has opportunities to learn. So the second factor is what happens to the individual—the sort of the environment in which he is brought up. If an individual is handicapped (受阻碍) environmentally, it is likely that his brain will stop to develop and he will never attain the level of intelligence of which he is capable.

    The importance of environment in determining an individual's intelligence can be proved by the identical twins, Peter and John. When the twins were three months old, their parents died, and they were placed in separate foster (寄养) homes. Peter was reared by parents of low intelligence in an isolated community with poor educational opportunities. John, however, was educated in the home well-to-do parents who had been to college. This environmental difference continued until the twins were in their late teens, when they were given tests to measure their intelligence. John's IQ was 125, twenty-five points higher than the average and fully forty points higher than his brother.

【写作内容】

1)以约30个词概括短文的要点;

2)然后以约120个词就“环境与人的智力发展”的主题发表看法,并包括如下要点:

a.你是否赞同“环境决定智力的发展”这一观点?为什么?

b.请举出具体事例说明你的观点;

c.你认为如何才能最大限度地发展智力?

【写作要求】

1)写作过程中不能直接引用原文语句;

2)作文中不能出现真实姓名和学校名称;

3)不必写标题。

【评分标准】

内容完整,语言规范,语篇连贯,词数适当。