问题 多选题
如图所示,理想变压器原副线圈匝数之比为4:1,原线圈接入一电压为u=220sin100πtV的交流电源,副线圈接一个R=27.5Ω的负载电阻.则下述结论正确的是(  )

A.副线圈中电压表的读数为55V

B.副线圈中输出交流电的周期为0.01s

C.原线圈中电流表的读数为0.5A

D.原线圈中的输入功率为110W

答案

AC

多项选择题
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This message is to inform all the children that Santa's post office in Himmelpfort, Germany, is open to receive your holiday wishes. That means you can mail your letters to Santa about 6 weeks sooner than that last year. Santa knows you've been good and wants to make sure he and his helpers receive your wish list earlier.

Eight post offices are organized across Germany to answer all letters children send. This year they plan to receive over 250,000 letters. Though the letters fly from over 80 different countries, Santa and his helpers can understand and make sure to answer all the letters.

In 1984, two children from Berlin sent their wish lists to Himmelpfort after spending vacation there. Their letters were answered by postal employees and later Himmelpfort increased its helpers to meet the needs of increased mail traffic. Year after year, Santa and his crew use an eco­friendly powered vehicle to collect the thousands of letters he receives from young boys and girls. The great news for this year is that if you come to the beautiful town of Himmelpfort, you can drop off your letter and visit Santa in person, from Tuesdays to Thursdays until Christmas Eve.

Santa does not currently have an e­mail, Twitter or a Facebook account. He believes in old­fashioned communication. So get out your paper and write your wish list. Just make sure your letter is clear so you can receive an official response, send your letters to:

Santa

Christmas Post Office

Himmelpfort, Germany 16798

小题1:This year Santa and his helpers ________.

A.are eager to receive more wishes

B.keep traveling around 80 countries

C.are able to receive kids' letters earlier

D.answer most of the letters from kids小题2:From the 3rd paragraph, we know that ________.

A.post offices send kids all the presents they ask for

B.children from Berlin like spending holidays in Himmelpfort

C.Santa uses a powered vehicle because of the heavy mail traffic

D.children can visit Santa in the flesh before Christmas Eve this year小题3:Santa doesn't have social communications online probably because he ________.

A.is not sure about the online security

B.trusts traditional ways of communication

C.prefers official and formal letters

D.thinks written letters are clearer than e­mails小题4:This text is intended for ________.

A.tourists coming to Himmelpfort

B.teenagers preferring writing letters

C.parents preparing for Christmas

D.children planning to write to Santa