在微波炉是人类为解决人类在太空中生活需要加热食品发明的新型炉_爱下问搜题

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问题选择题

在微波炉是人类为解决人类在太空中生活需要加热食品发明的新型炉灶，现在这种炉灶已经走进了寻常百姓家，微波炉中的变压系统中有如图所示的变压器，当原线圈绕组n₁上加220V、50H_Z的正弦交流电压时，在副线圈绕组n₂上产生了3.4V的低压交变电压，在另一副线圈绕组n₃上产生2000V的高压交变电压，若微波炉中的变压器可以视为理想变压器，则其原、副线圈绕组中的下列物理量一定相等的是（　　）

①交流电的频率； ②交变磁通量的最大值； ③交流电的传播速度； ④交变磁通量的变化量； ⑤交流电的最大值； ⑥交流电的周期； ⑦电功率．

A．①③⑤⑥⑦

B．①②③④⑦

C．①②④⑥⑦

D．②③④⑤⑥

答案

根据电磁感应原理可知，由原线圈绕组n₁交变电流产生的磁通量变化全部通过变压器的铁芯传给副线圈，理想变压器的原线圈的磁通量的变化率与副线圈中磁通量变化率相同，则电流的频率也相同，交变磁通量的最大值相同，交流电的传播速度相同，交变磁通量的变化量相同，当理想变压器的原副线圈匝数相等时，原副线圈电压相等，则电压的最大值相等，若匝数不等，则最大值不等，理想变压器是理想化模型，一是不计线圈内阻；二是没有出现漏磁现象．所以原副线圈的功率相等．

故选B．

阅读理解

B

Every afternoon in South Korea, when school and work finish, over 100,000 people meet on the Internet to play a game called Lineage. They meet in a virtual（虚拟的） world 500 years in the past. They form teams and fight for justice and money. They are part of one of the Internet's many online gaming communities. The people who play these games are called gamers. Often they meet in 24-hour cafés to play Lineage, as well as other games such as Diablo, StarCraft and Counter Strike. Most gamers just play for fun, but for some people, it can become an obsession （着迷）.

When gaming becomes an obsession it can become dangerous. In Hong Kong, a seventeen-year-old boy died as a result of playing his favourite game in the café where he worked. After working for eight hours, he often stayed at the café and played Diablo II. On some nights he slept for only two hours. In May 2002, he was found unconscious at a computer after playing all night. When he died later in hospital, doctors said it was because he was exhausted.
In Korea, the dangers can come from other gamers. In the virtual world of Lineage, gamers can create new characters for themselves. High school students can become very powerful fighters and leaders. They play against doctors, businessmen and even members of dangerous gangs. But sometimes things that happen in the game affect real life. Gamers have been beaten up in real life by people they have killed online!
56. How many people play Lineage when school and work are over every day in South Korea?
57. What do people do in the virtual world of Lineage?
58. The online games mentioned in the passage are ________.
59. What does the underlined word “exhausted” mean?
60. What does the passage mainly talk about?

填空题

教育学的产生和发展大体上经历了（）阶段、（）阶段和（）阶段。