题干

小华到河边游玩,在河中发现如图甲所示的装置,顺着导线小华来到河边的一个小屋,在屋内发现了图乙所示的小装置,屋里的叔叔告诉小华,这两个装置组成了防汛报警器。以下说法正确的是(    )


A:当水位升高时,浮子A上浮使触点K闭合,电磁铁中有了电流,电磁铁有磁性,把衔铁吸引下来,灯泡所在电路接通,灯亮,发出报警信号。

B:电磁继电器是通过电磁铁,利用低电压、强电流的通断,来控制高电压、弱电流电路的装置。

C:通过电磁感应现象,人们制造并应用电动机,电磁感应就是通电导体周围会产生磁场。我们可以通过右手定则判断磁场的方向。

D:本图中的灯泡是将磁能转化为光能的装置。弱将电磁铁中的铁棒换成铜棒,当水位上升时,由于电磁铁磁性不足,小灯泡可能不会亮。

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A

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    Experts say that, among young Internet users, it's not boys who create most web content. The pioneers of the Internet at the moment are the girls.

    According to Jenny Baker, whose hobbies are designing icons(图示), most boys just aren't patient enough for blogging, uploading photographs, and creating their own websites. Jenny posts her pictures on her own website, and believes that most boys don't often have their own sites. She thinks it's mainly girls.

    And Jenny is right. A study shows that, among Internet users aged 12 to 17, a lot more girls blog than boys (35 percent of girls compared with 20 percent of boys). A lot more girls also work on their web pages (32 percent of girls compared with 22 percent of boys). Girls are also ahead of boys in working on websites for other people.

    Some girls have their own teenage podcasts(播客)which have become very successful and sometimes the creators have their own TV shows too. When asked what they think about the study that shows girls are more active on the web, they say that they're not surprised because girls are very creative, and sometimes more creative than boys.

    Other girl have started interactive(交流的)e-zines with articles written for girls by girls. “Girls from everywhere read our articles, and they ask lots of questions,” they say. “I think girls like to help other people more.” One expert said: “If boys were more interested in helping other people, the numbers would be different.”

    But if girls are more interested in computers, why do women only have 27 percent of computer-related jobs? Maybe this will change in the future—after all, girls like these will be in the job market before too long.