问题 选择题

图甲左侧的调压装置可视为理想变压器,负载电路中R=55Ω,A、V为理想电流表和电压表.若原线圈接入如图乙所示的正弦交变电压,电压表的示数为110 V,下列表述正确的是(   )

A.电流表的示数为2A

B.原、副线圈的匝数比为1∶2

C.电压表的示数为电压的有效值

D.原线圈中交变电压的频率为100Hz

答案

AC

题目分析:电流表的电流为,A正确;由乙图知,原线圈电压有效值为220V,电压表的读数为有效值,C正确;原、副线圈匝数比,B错误;交流电的周期为0.02s,则频率为50Hz,D错误

点评:本题主要考查了变压器的电压、电流与匝数比的关系,根据图像与峰值、有效值的关系先读出有效值、周期,再由变压器原理判断其他问题

单项选择题
阅读理解

Visiting the Embassies of Washington, D.C.

Washington, D.C.is known for its many museums and government buildings.It is also home to embassies(大使馆)from more than 170 countries. Many of these buildings around the city have interesting histories. Some embassies are in large historical homes. Others were built more recently to show the building desihgn of their countries. Many embassies hold special cultural(文化)events.

The Embassy of Uzbekistan

It is in a richly decorated(装修)home built in 1906 by a wealthy banker, Clarence Moore. But Mr Moore did not live to enjoy his house for very long. He died on board the ship Titanic, which sank 1912·This building served as the Canadian Embassy before Uzbekistan bought it in 1996.

The Embassy of Finland

The Italian Embassy is near Massachusetts Avenue. Nearby, the Embassy of Finland looks like it is built out of blocks of glass.Its design is modern,but it fits in nicely with the natural environment around it.A screen of plants covers part of the front of the building.Inside.visitors Can look through large glass windows deep into the wooded areas of Rock Creek Park. The Finnish Embassy holds many interesting exhibits.

The Embassy of France

It is in a gated area off Reservoir Road.The embassy’s cultural center, La Maison Francaise, organizes many cultural events.Also.if you are very lucky, you might be invited to a party at the home of the French ambassador(大使).This extraordinary home in the Kalorama neighborhood looks like a palace。Organizations like the Washington Opera sometimes hp1d events in this beautiful house。

The International Center

Last month,China opened a new embassy in the area of Washington called the International Center.C.C.Pei and L.C。Pei designed the building.Measuring more than 10.000 square meters,this is One of the biggest embassies in Washington.C.C.Pei said the areas of plants around the embassy were to present people a natural and calming design.

小题1:Which embassy was once a large historical home?

A.The International Center.

B.The Embassy of Finland.

C.The Embassy of France.

D.The Embassy of Uzbekistan.小题2:What can we learn about the International Center from the text?

A.It once belonged to a rich banker.

B.It was built out of blocks of glass.

C.It stands in the Kalorama neighborhood.

D.It is a newly—constructed building.小题3:At the Embassy of France,you can      .

A.see many exhibits of great interest        

B.attend events in La Maison Francaise

C.invite the French ambassador home     

D.visit its designers C.C.Pei and L.C.Pei

小题4:This text is most probably taken from

A.a science magazine

B.a medical report

C.a travel guide

D.a history textbook