题干

发电机的转子在匀速转动过程中,下列物理量没有发生改变的有(  )

A:穿过线圈的磁通量

B:线圈中产生的感应电动势

C:闭合回路中的电流

D:闭合回路中电流变化的周期

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答案(点此获取答案解析)

D

同类题3

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    I remember that it was a fall morning when the orchestra teachers came into Miss Newell's third-grade classroom. “You have hands for the viola (中提琴),” Miss Ciano told me. I was excited because my hands were finally good for something. I told my parents I wanted to play, and naturally, they agreed.

    Since I first touched the viola, I haven't been able to put it down. Ignoring the difficulty, I am pulled closer to it each day.

    Classical music is truly my best friend. It is the trusted friend of every man, woman and child. Various feelings are expressed in classical music. I discovered that when I was eleven and played a Bach cello concerto (大提琴协奏曲) in a competition, the first movement was joyful, but the second movement was mysterious and full of pain. From that piece, I learned that music expressed not only feelings, but also sudden mood changes. By listening to classical music, I know that someone else share these feelings. Since I am lucky enough to be able to play classical music, I am comforted when I am upset. It gives me a way to escape from my problems for a short period. Classical music can express my joy, sadness and anger.

    Now look at that fall day and think how gullible I was for believing that anyone, even music teachers, could tell if hands were perfect for a certain instrument. I'm certain they told me I had “viola hands” not because they were fortune-teller, but because there was a lack of violists in our district. Classical music is one of the best things that ever happened to mankind. If you get introduced to it in the right way, it will become your friend for life.

同类题4

阅读下面文言文,完成小题。

    建兴①元年,封亮②武乡侯,开府治事。顷之,又领益州牧。政事无巨细,咸决于亮。南中诸郡,并皆叛乱,亮以新遭大丧,故未便加兵,且遣使聘吴,因结和亲,遂为与国。三年春,亮率众南征,其秋悉平。军资所出,国以富饶,乃治戎讲武,以俟大举。五年,率诸军北驻汉中。

    六年春,扬声由斜谷道取郿,使赵云、邓芝为疑军,据箕谷,魏大将军曹真举众拒之。亮身率诸军攻祁山,戎陈整齐,赏罚肃而号令明,南安、天水、永安三郡叛魏应亮,关中响震。魏明帝西镇长安,命张郃拒亮,亮使马谡督诸军在前,与邰战于街亭。谡违亮节度,举动失宜,大为张郃所破。亮拔西县千余家,还于汉中,戮谡以谢众。上疏曰:“臣以弱才,叨窃非据,亲秉旄钺以历三军,不能训章明法,临事而惧,至有街亭违命之阙,箕谷不戒之失,咎皆在臣授任无方。臣明不知人,恤事多暗,《春秋》责帅,臣职是当。请自贬三等,以督厥咎。”于是以亮为右将军,行丞相事,所总统如前。

    冬,亮复出散关,围陈仓,曹真拒之,亮粮尽而还。魏将军王双率骑追亮,亮与战,破之,斩双。七年,亮遣陈式攻武都、阴平。魏雍州剌史郭淮率众欲击式,亮自出至建威,淮退还,遂平二郡。诏策亮曰:“街亭之役,咎由马谡,而君引愆,深自贬抑,重违君意,听顺所守。……方今天下骚扰,元恶未枭,君受大任,干国之重,而久自绝损,非所以光扬洪烈矣。今复君丞相,君其勿辞。”

    九年,亮复出祁山,以木牛③运,粮尽退军,与魏将张郃交战,射杀邰。十二年春,亮悉大众由斜谷出,以流马运,据武功五丈原,与司马宣王对于渭南。亮每患粮不继,使己志不申,是以分兵屯田,为久驻之基。耕者杂于渭滨居民之间,而百姓安堵,军无私焉。相持百余日。其年八月,亮疾病,卒于军,时年五十四。

(取材于《三国志·蜀志·诸葛亮传》)

【注释】①建兴:蜀汉后主刘禅的年号,建兴元年为223年。②亮:诸葛亮(181-234)字孔明。刘备死后,继续辅佐后主刘禅治理蜀国,并大力伐魏,以图统一。③木牛:与下文的“流马”都是古代运输工具,为诸葛亮所创。