题干

小文用如图所示的电路探究“电流与电阻”的关系,可选器材如下:电压恒为4.5V的电源,“20Ω 1A”的滑动变阻器,5Ω、10Ω、15Ω、20Ω的定值电阻.实验时,控制电阻两端电压为2V.当用20Ω的电阻替换15Ω的电阻进行实验时,发现,调节滑动变阻器,无法使电压表的示数达到控制电压,经检査,电路连接无误,且元件完好,下列分析中错误的是(   )

A:设定的定值电阻两端电压2V偏低

B:R0的最大阻值20Ω偏小

C:滑动变阻器允许通过的最大电流1A不够大

D:电源电压4.5V偏高

上一题 下一题 0.0难度 选择题 更新时间:2018-02-08 03:24:27

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C

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阅读理解

    Money is the root of all evil (邪恶) and new study claims there may be some truth behind the saying. Scientists at the University of California Berkeley, US, announced on February 27 that rich people are more likely to do immoral things, such as lie or cheat, than poorer people. The scientists did a series of eight experiments. They published their findings online in the Proceedings of the National Academy of Sciences (PNA《美国国家科学院院刊》).

    They carried out the first two experiments from the sidewalk near Berkeley. They noted that drivers of newer and more expensive cars were more likely to cut off other cars and pedestrians at crosswalks. Nearly 45 percent of people driving expensive ears ignored a pedestrian compared with only 30 percent of people driving mow modest cars.

    In another experiment, a group of college students was asked if they would do immoral things in various everyday situations. Examples included taking printer paper from work and not telling a salesperson when he or she gave back more change. Students from higher — class families were more likely to act dishonestly.

    According to the scientists, rich people often think money can get them out of trouble. This makes them less afraid to take risks. It also means they care less about other people's feelings.

    Finally, it just makes them greedier. “Higher wealth status seems to make you want even more, and that increased want leads you to bend the rules or break the rules to serve your self- interest,” said Paul Piff, lead scientist of the study.

    Piff pointed out that the findings don't mean that all rich people are untrustworthy or all poor people honest. He said the experiments were to show how people living in different social situations express their instincts(本能)and values in different ways.