题干

某矩形线圈在匀强磁场中匀速转动,产生的感应电动势为e=Emsinωt.若将线圈的转速增加1倍,保持其他条件不变,则产生的感应电动势为(    )

A:e=Emsin 2ωt

B:e=2Emsin  2ωt

C:e=2Emsin  4ωt

D:e=4Emsin  2ωt

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B

同类题1

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    叶义问,字审言,严州寿昌人。建炎初,登进士第。调临安府司理参军。范宗尹为相,义问与沈长卿等疏其奸。为饶州教授,摄郡。岁旱,以便宜发官仓赈民,提刑黄敦书劾之,诏勿问。前枢密徐俯门僧犯罪,义问绳以法,俯本欲举义问,怒甚,俯乃袖荐书与之。

    知江宁县。召秦桧所亲役,同僚不可,义问曰:“释是则何以服他人。”卒役之。通判江州。豫章守张宗元忤桧,或中以飞语,事下张常先。宗元道九江,常先檄义问拘其舟,义问投檄曰:“吾宁得罪,不为不祥。”常先白桧,罢去。

    桧死汤思退荐之上记其尝言范宗尹召至言台谏废置在人主桧亲党宜尽罢逐以言得罪者宜叙复擢殿中侍御史。枢密汤鹏举效桧所为。植其党周方崇、李度,置籍台谏,锄异己者。义问累章劾鹏举,有“一桧死一桧生”之语,并方崇等皆罢之。又言:“凡择将遇一阙,令枢密院具三名取上旨,则军政尽出掌握。”

    上闻金有犯边意,遣义问奉使觇之,还奏:“彼造舟船,备嚣械,其用心必有所在,宜屯驻沿海要害备之。”金主亮果南侵。命视师,义问素不习军旅。至镇江,闻瓜洲官军与敌相持,大失措,乃役民掘沙沟,植木枝为鹿角御敌,一夕潮生,沙沟平,木枝尽去。会建康留守张焘遣人告急,义问乃遵陆,云往建康催发军,市人皆媟骂之。又闻敌据瓜洲,采石兵甚众,复欲还镇江,诸军喧沸曰:“不可回矣,回则有不测。”遂趋建康。已而金主亮被弑,师退,义问还朝,力请退,遂罢。

    隆兴元年,中丞辛次膺论义问“顷护诸将几败事,且以官私其亲”。谪饶州。乾道元年,诏自便。六年卒,年七十三。

(选自《宋史·叶义问传》,有删减)

同类题4

任务型阅读

    Some people think only school children do not agree with their parents. However,it is not true.____If it's hard for you to communicate with your parents,don't worry about it.Here are some advice for you to bridge the generation gap(消除代沟).

    ____Don't get to your parents when you are angry.Your parents possibly won't consider your ideas if you are shouting at them. And you can't express yourself well if you are angry. Go to some place to cool off.

    Try to reach a compromise(和解).____You can keep your disagreement and try your best to accept each other. Michael's mother didn't agree with him about buying a motorcycle. They argued over it. But they finally came to a compromise. Michael bought the motorcycle, but only drove it on certain days.

Of course, your parents might refuse to compromise on something. In these situations, it is especially important to show love and respect to them.____

    Talk about your values(价值观). The values of your parents are probably different from those of your own.____ Understanding your values might help them see your purposes in life.

    A good relationship with your parents can make you a better and happier person. It is worth having a try.

A. Don't argue with your parents.

B. Tell your parents what you care about, and why.

C. Make sure you understand why you are unhappy.

D. Showing respect will keep your relationship strong.

E. Perhaps you and your parents disagree on something.

F. Communication is a problem for parents and children of all ages.

G. If you don't think you can speak to them at the moment, try writing a letter.