问题 多选题

如图所示,理想变压器的原副线圈的匝数比为4:1,原线圈接有u=311sin100πt V的交变电压,副线圈上接有定值电阻R、线圈L、灯泡L1及理想电压表V,以下说法正确的是

[ ]

A.副线圈中电流的变化频率为50HZ

B.灯泡L1两端电压为55V

C.若交变电压u的有效值不变,频率增大,则灯泡L1的亮度将变暗

D.若交变电压u的有效值不变,频率增大,则电压表V的示数将减小

答案

AC

阅读理解

阅读理解。

         Chinatown is the name given to an area in the middle of London. It is just between Leicester Square

and Shaftsbury Avenue. Gerrard Street is at the center and is the most important street in the area. There

is a large Chinese community (社区) with a lot of Chinese restaurants, Chinese supermarkets and shops in

this street.

         In the 1950s, it was a poor area and everything was very cheap. At the same time, the world rice

market changed and thousands of farm workers in Hong Kong lost their jobs. They began arriving in London

to look for work. They found jobs in the restaurants in this area. Many British people liked Chinese food, and

the restaurants were popular.

         These restaurant workers often worked 17 hours a day and had no time to learn English. As more

Chinese arrived, more shops and businesses grew up. Wives came and joined their husbands and children

came and joined their fathers. The community grew, and Chinatown was born.

         In the 1970s and 1980s, British-born Chinese started to have a better education and this brought

economic (经济的) success to the area. Many families moved out of Chinatown, and there was more space

for businesses. Gerrand Street became a street only for visitors and was soon a popular place for tourists.

        Now everyone knows about London's Chinatown. During the Chinese New Year, the streets are seen

with flags and thousands of Chinese go into the streets. For most of the year, though, Londoners and tourists

go there mainly for the food in the Chinese restaurants. The best restaurants are the ones where the Chinese

eat.

1. Is this Chinatown in the middle of London?

   ________________________________________________

2. Was the area rich or poor in the 1950s?

   ________________________________________________

3. Why did the restaurant workers have no time to learn English?

   ________________________________________________

4. When did British-born Chinese start to have a better education?

   ________________________________________________

5. What are the main points about Chinatown in this passage?

   ________________________________________________

单项选择题 A1/A2型题