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问题 选择题

理想变压器的原线圈接正弦式电流，副线圈接负载电阻R，若输入电压不变，要增大变压器的输出功率，可行的措施有：（ ）

A．只增大负载电阻R的阻值

B．只减小负载电阻R的阻值

C．只增大原线圈的匝数

D．只增大副线圈的匝数

答案

BD

题目分析：增大变压器的输出功率就是增大负载电阻上消耗的电功率，因为P=，故减小负载电阻R和增大副线圈的电压都可以，而增大副线圈的匝数正是增大了副线圈上的电压，故BD是正确的，A、C是不对的。

单项选择题

ADL评定的内容不包括（）。

A、运动方面

B、自理方面

C、交流方面

D、能量代谢方面

E、家务劳动方面
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单项选择题

Many people are surprised when they find the Internet(因特网)was set up in the 1960s. At that time, computers were large and expensive. Computer networks(网络) didn’t work well. If one computer in the network broke down, then the whole network stopped. So a new network system (系统) had to be set up. It should be good enough to be used by many different computers. If a part of the network was not working, information could be sent through another part. In this way computer network system would keep on working all the time.
At first the Internet was only used by the government, but in the early 1970s,universities(大学) ,hospitals and banks were allowed(允许) to use it too. However, computers were still very expensive and the Internet was difficult to use. By the start of the 1990s, computers became cheaper and easier to use.
Today it is easy to get on-line(上网) and it is said that millions of people use the Internet every day. Sending e-mail is more and more popular among students.
The Internet has now become one of the most important parts of people’s life.

The word" information" may probably mean

A. letter


B. message

C. number
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