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如图所示，理想变压器的原副线圈匝数比n1：n2=1：10，副线圈与阻值R=20Ω的电阻相连．原线圈两端所加的电压u=20sin20πt(V)，则（　　）

A．副线圈输出交流电的频率为10Hz

B．交流电压表的示数为20V

C．电阻R上消耗的电功率为2kW

D．原线圈中电流的最大值为100A

答案

AC

阅读理解

阅读理解。         
        Different weather makes people feel different. It influences (影响) health, intelligence (智力) and
feelings.      
         In August, it is very hot and wet in the southern part of the United States. People there have heart trouble
and other kinds of health problems during this month. In the Northeast and the Middle West, it is very hot at
some times and very cold at other times. People in these states have more heart trouble after the weather
changes in February or March.
         The weather can also influence intelligence. For example, in a 1983 report by scientists, IQ (智商) of a
group of students was very high when a very strong wind came, but after the strong wind, their IQ was 10%
lower. The wind can help people have more intelligence. Very hot weather, on the other hand, can make it lower. Students in many schools of the United States often get worse on exams in the hot months of the year (July
and August).Weather also has a strong influence on people's feelings. Winter may be a bad time for thin people.
They usually feel cold during these months. They might feel unhappy during cold weather. But fat people may
have a hard time in hot summer. At about 18℃, people become stronger.
          Low air pressure (气压) may make people forgetful. People leave more bags on buses and in shops on
low-pressure days. People feel best at a temperature of about 18℃.
          Are you feeling sad, tired, forgetful, or unhappy today? It may be the weather's problem.

1. ________ can cause problems on health.
[ ]
A. Hot and wet weather
B. A strong wind
C. Warm weather
D. Low air pressure
2. A report shows that people may have more intelligence when ________ comes.
[ ]
A. rain
B. a strong wind
C. very hot weather
D. low air pressure
3. According to (根据) the writer, fat people may feel bad in ________ weather.
[ ]
A. cold
B. cool
C. warm
D. hot
4. The writer wants to tell us that ________.
[ ]

A. hot and cold weather influences all people in the same way
B. weather influences people's behaviour
C. IQ changes when weather changes
D. people feel good on low pressure days

5. The best title (标题) for this passage is ________.
[ ]
A. Hot Weather Causes Health Problems
B. Different Weather Makes People Feel Bad
C. Weather Influences Feelings
D. Weather Influences Health, Intelligence and Feelings
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单项选择题

“阳历”与“阴历”这两个词虽然大家都熟悉，但是仍有不少人对其理解有误。有人认为阳历来自外国，这是不对的。我们从甲骨文中可以看出我国三千年前就有十三月的名称，已经是阴阳历并用。《书经•尧典》上说“期三百有六旬有六日以闰月定四时成岁”。三百有六旬有六日就是阳历年；以闰月定四时成岁乃是阴阳历并用。西洋在希腊罗马时代也夹用阴阳两历，和我国原是一样的。阴历是完全依据月亮的[a]，阳历则完全依据太阳的[b]。月亮绕地球一周所需时间为29.53059天，就是29天12小时44分3秒。地球绕太阳一周所需时间为365.242216天，即365天5小时48分46秒。两个小数不能相互除尽，要把它们合起来非常困难。但我国在春秋时代已知道十九年七闰的方法，把阴阳二历调和得相当成功。
二十四节气也是我国古代历法的特点。节气是完全跟太阳走的，可称阳历的一部分。地球绕日因为昼夜长短太阳高低的不同，所以一年有春夏秋冬四季。二十四节气中，十二个为气，十二个为节。节应在月初，气应在月中，譬如立春为阴历正月之节，雨水乃正月之气等等。二十四节气是一个循环，有天，一节一气平均 30天多一点。而阴历一个月只有29天有余。过了若干时候必会有月份单有节而无气，或单有气而无节。这有节无气的月份就叫做[ ]。这样安排的好处是阴阳两历的周期都照顾到了，维持了一个月中晦朔弦望，和一年中的春夏秋冬。它的缺点是年度长短不同，平年只有354天，闰年多一个月就有384天，计算极不方便。

下列各项中，所说的不属于阴阳历并用的是哪一项( )

A．一年分四季，四季定出二十四个节气

B．年五四季不成岁，月有朔望倍觉亲

C．十分成功地运用十九年七闰的方法

D．根据月亮绕地球、地球绕太阳的运行来制定历法
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