Cuộn sơ cấp của 1 máy biến thế có 4000 vòng, cuộn thứ cấp có 12000 vòng đặt ở 1 đầu đường dây tải điện để truyền đi 1 công suất điện là 12000kW. Biết hiệu điện thế ở hai đầu cuộn thứ cấp là 120kV.

a) Tính hiệu điện thế đặt vào 2 đầu cuộn sơ cấp?

b) Biết điện trở của tổng bộ đường dây là 200 ôm. Tính công suất hao phí do tỏa nhiệt trên đường dây.

c) Muốn công suất hao phí giảm bằng 1/2 thì phải tăng hiệu điện thế lên bao nhiêu?

Choose the right word from the box to fill each blank to complete the following sentences.

1. Is the permit ………………………?

2. What are the ………………………of the room?

3. It was very ………………………of you to send the flowers.

4. Her speech made a tremendous ………………………on everyone.

5. Alarms are ………………………at strategic points around the prison.

6. Old people are usually more ………………………than young people.

7. The government has prohibited the import of ………………………chemicals.

8. Spending less money is the ………………………answer to his financial problems.

9. The public should be ………………………in how to use energy more effectively.

10. The government is pressing for immediate ………………………of the changes.

Thu gọn

Put the following words in the correct order.

1. all / It is / that students / important / should / the lectures / attend /.  

………………………………………………………………………………………………………………………………

2 will look / Who / business affairs / are away / your / while / you /?

………………………………………………………………………………………………………………………………

3. dirty. I’d better / My shoes / before / I / take them off / come in / are /. 

………………………………………………………………………………………………………………………………

4. is going to / you’re / Who / look after / when / at work / your children /? 

………………………………………………………………………………………………………………………………

5. coming from / At / flowers coming from / the flower market, / are more expensive than / the farms / around here / this company / the ones /.

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

Read the following passage and choose A, B, C and D for each of the following questions below.

Radar is an electronic device that can “see” great distances (1) ……………………fog, rain, snow, clouds and darkness. It can find and accurately (2) ……………………missiles, air-craft, ships, cities, rainstorms, and mountains. Radar uses radio waves (3) ……………………light waves, which the human eye uses in seeing. This (4) ……………………it likely for radar to locate many kinds of object at greater distances (5) ……………………the eye can see.

Radar became an (5) ……………………military device during World War II. Today, networks of radar lookout stations guard the United States and Canada 24 hours a day (6) ……………………long-range missiles and airplanes. Petrol planes and ships search the oceans (6) ……………………radar for hostile ships and aircraft. Airports use radar to (7) ……………………planes safely to earth in fog or storms. Radar helps weatherman warn of (8) ……………………hurricanes and tornadoes.

1.    A. despite of    B. despite    C. although    D. even though

2.    A. locate   B. locating    C. located     D. location

3.    A. instead    B. instead of    C. in spite of    D. despite of

4.    A. make    B. makes   C. do     D. does

5.    A. more than     B. than    C. that   D. as

6.    A. import     B. importance    C. important    D. importantly

7   . A. against    B. for    C. to    D. with

8.    A. by     B. with    C. on    D. at

9. A. guiding    B. guide     C. scouting     D. scout

10.  A. approach   B. approached    C. to approach    D. approaching

Choose the right word from the box to fill each blank to complete the following sentences.

1. Is the permit ………………………?

2. What are the ………………………of the room?

3. It was very ………………………of you to send the flowers.

4. Her speech made a tremendous ………………………on everyone.

5. Alarms are ………………………at strategic points around the prison.

6. Old people are usually more ………………………than young people.

7. The government has prohibited the import of ………………………chemicals.

8. Spending less money is the ………………………answer to his financial problems.

9. The public should be ………………………in how to use energy more effectively.

10. The government is pressing for immediate ………………………of the changes.