Ba điện trở R 1 = 10 , R 2 = R 3 = 20  được mắc song song với nhau vào giữa hai
điểm A và B có hiệu điện thế là U
1.Tính điện trở tương đương của đoạn mạch.
2.Biết cường độ dòng điện qua R 1 có giá trị là 2,4 A. Tìm hiệu điện thế U giữa hai đầu đoạn
mạch và cường độ dòng điện chạy qua mạch chính và các mạch rẽ còn lại.
Bài 3:Một đoạn mạch gồm một bóng đèn có ghi 9V-4,5W được mắc nối tiếp với một biến
trở và được đặt vào HĐT không đổi 12V (Hình vẽ).Điện trở của dây nối và ampe kế rất nhỏ.
a/.Bóng đèn sáng bình thường,tính điện trở của biến trở và số chỉ của ampe kế.
b/. Tính điện năng tiêu thụ của toàn mạch trong thời gian 15 phút.

1. They .......................................................................their work. ( already/ finish)
2. The children....................................at this time yesterday.(swim)
3. She .................................................this shirt yesterday. (buy)
4. Look! The students..........................................in the rain. (play)
5. The Pikes .............................................in New York for 20 years. ( live)
6. He ........................................................a letter last week. (send)
7. They..................................................their work yet.( not finish)
8. ........................................you ever...............................................turkey? (eat)
9. He .................................................................her last wªk. ( not visit)
10. We ...................................................since 7 o’clock. (learn)
11. Nam.........................................................a letter from his pen pal. (just/ receive)
12. This is the most interesting film I ..................................................(see)
13. Mr Long ..............................................a house recently. (build)
14. I ...........................................................a doctor in the future. ( become)
15. It is the fist time I ...............................................a motorbike. (ride)
16. They..................... at this school for 4 years. (teach)
17. How many lessons.......................................you......................................? (study)
18. They (get) …………………………………………………………………on the scale
now.
19. The earth (circle) ………………………………the Sun once every 365 days.
20. Rivers usually (flow)………………………………………………… to the sea.
21. Don’t worry. I (give) …………………him your message when I (see)……………
him.
22. ................ the children (play)………………………………… in the park at the
moment?
23. I don’t know. But she always (go) ...................................... to the church on
Sundays.
24. The students (not be) ............................................ in class at present.
25. She always (wash) ........................................................ the dishes after meals.
26. My mother sometimes (buy) ........................................... vegetables at this market.

27. It (rain) ......................................... much in summer. It (rain)
..................................... now.
28. Daisy (cook) ............................................ some food in the kitchen at present. She
always (cook) ...................................................... in the morning.
29. I ......................................................him when he was riding to school. ( see)
30. We .................................................................Math and literature tomorrow. (have)
31. Nam and Ba........................................................a bath yet. ( not take)
32. He always.....................................................to school on time. (go)
33. The students .................................the lesson now. ( write)
34. We ( watch ) ………..............................…….T.V every morning .
35. I (do ) ……………….....................……my homework every afternoon .
36. Mai and Lan ( play ) ……...............…………….games after school .
37. Vy ( listen ) ………..........................………to music every night .
38. Where ( be ) …………................……..your father now ?
39. He ( read ) ………….........……..a newspaper .
40 . What ……….............….you ( do ) ………………? I ( be ) ……….a student .
41 . Where ………….you ( go ) …………….............….now ?
42. I (go ) ………………to the market yessterday.
43 . She is cooking and we ( do ) ……………………..the housework .
44 . He isn`t in the room . He ( play ) …….....................…………..in the garden .
45. Look ! The birds ( fly ) ………………………….
46 . I ( go ) ……….to school by bus every day , but today I ( go ) …………..to school by bike
.
47 . Listen ! Mai ( sing ) ………………………….
48. My father .........................a magazine while my brothers were doing the homework. (read)
49. She always .................Vietnamese songs but tonight she..................an English song. (sing)
50. They..........................while I was learning the lesson. (play)
51. Mr Peter.................................for this company since he moved to London. (work)
52. When I came, she.....................................................dinner. ( eat)
53. Steve often ( smoke ) ….....................……………….10 cigarettes a day .
54 . We usually ( have ) ………….............…………dinner at 7: 00
55 . Anne ( wash ) ……………..............…….her hair twice a week .
56 . Jane ( teach ) …………….............……English to children .
57 . You ( meet ) …………….................................…….a lot of people .
58 . He often ( go ) ……………….........………….to the cinema .
59. ...............................you...........................that work yet? ( finish)
60. I..............................Rock music. ( not like)
61. ..........................you ever..........................by plane? (travel)
62. ...........................he .......................a gift yesterday? ( receive)
63. Two years ago , she ( teach ) …….............…………at a village school .
64 . We ( travel ) ……………………………to Hue next week .
65 . What ……………........you ( do ) ……........……………yesterday morning .
66. Could you ( show ) ……………………me the way to the bus stop .
67 . Lan and Hoa ( go ) …………..............……..to the post office now.
68 . Liz ( need ) ……………...............….some stamps and envelopes .
69 . Hoa ( mail ) ………….........................……….this letter tomorrow .
70 . I need ( buy ) ……………..a phone card .
71 . He ( phone ) …………………….his parents three or four times a week .
72 . Nam wants ( send ) ………….............…………..this postcard to his penpal 73 . We would like ( visit ) ………................……………Ngoc Son Temple .
74 . My hair is dirty . I ( wash ) …................…………….it .
75 . We ( have ) ………………………an English test tomorrow.
76 . They usually ( paint ) ……………….............……..their house blue .
77 . My father ( buy ) ……………………..a new car 2 months ago .
78 . Nam ( help ) …………………...............…his father repair the radio at this time
79. Let us ( go ) …………………to the English club .
80 . I ( do ) ……………….my math homework at the moment .
81 . Next year , my sister ( be ) ………………..a teacher .
82 . When they ( be ) ……young , they ( leave ) ……….their family and ( go ) ………to Ho Chi Minh
city .
83 . When ………………..Thomas Edison ( die ) …………………? In 1931 .
84. We are interested in........................................film. ( watch)
85. I am used to.........................................up late. ( stay)
86. ...................................................English is important. (learn)
87. It is very difficult ...........................................English. ( study)
89. The crowd were cheering when Nam .........................................the race. ( win)
90. Ba is keen on ...............................................( paint)
91. We are happy ..............................................good marks. (get)
92. I am very tired. I ..........................................hard all day. ( work)
93. She ........................................................Ha Long Bay before. (already/ visit)
94. His father stppped..........................................cigarette two years ago. (smoke)
95. I suggest ....................to schoool or to work by bikes to save energy. (go)
96. It took him an hour............................these exxercises yesterday. ( do)
97. I am used to...................................up early every morning. ( get)
98. I ..........................................................him yesterday. ( not see)
99. Miss Hoa ........................................................... a new motorcycle. (just/ buy)
100. I ..................................my homework while my brother and sister.................................. TV. (do-
watch)