In larger commercial applications, central heating is provided through an air handler which incorporates similar components as a furnace but on a larger scale.

Hydronic and steam systems

Hydronic heating systems are systems that circulate a medium for heating. Hydronic radiant floor heating systems use a boiler or district heating to heat water and a pump to circulate the hot water in plastic pipes installed in a concrete slab. The pipes, embedded in the floor, carry heated water that conducts warmth to the surface of the floor where it broadcasts heat energy to the room above.

Hydronic systems circulate hot water for heating. Steam heating systems are similar to heating water systems, except steam is used as the heating medium instead of water.

Hydronic heating systems generally consist of a boiler or district heating heat exchanger, hot water circulating pumps, distribution piping, and a fan coil unit or a radiator located in the room or space. Steam heating systems are similar except no circulating pumps are required.

Hydronic systems are closed loop: the same fluid is heated and then reheated. Hydronic heating systems are also used with antifreeze solutions in ice and snow melt systems for walkways, parking lots and streets. They are more commonly used in commercial and whole house radiant floor heat projects, while electric radiant heat systems are more commonly used in smaller "spot warming" applications.

The Passive Voice

Present simple

passive subject	'to be'	past participle
Paper	is	made	from wood
Tigers	are	found	in India

Past simple

passive subject	'to be'	past participle
The bridge opened in	was	opened	in 1977
The pyramids	were	built	By the Egyptians

Future simple

passive subject	'to be'	past participle
The novel	will be	written	tomorrow

EXERCISE 1Complete the sentences using the given words as in the model:

Model hear

The music at the party was very loud and __________ from far away.

The music at the party was very loud and WAS HEARD from far away.

Arrest, wake, knock, check translate, find, drive, make, spend carry.

1. A decision will not _______________ until the next meeting.

2. That old building was dangerous. So it ___________ down.

3. When you go through customs, you luggage ___________ by the customs officer.

4. In the morning I _____________ by my alarm clock.

5. Next year her new book ______________ into a number of foreign languages.

6. John kicked a policeman, so he ____________.

7. After a long search the missing boy _____________ in the forest near the town.

8. Many people think that today too much money ________________ on arms. (arms - зд. оружие.)

9. The injured man couldn't walk, so he _____________ by the hospital orderlies.

10. I don't mind driving but I like when I _______________ by other people.

EXERCISE 2. Open the brackets using the verbs in Present , Past or Future Simple Passive .

1. Bread (to eat) every day. 2. The letter (to receive) yesterday. 3. Nick (to send) to Moscow next week. 4. I (to ask) at the lesson yesterday. 5.1 (to give) a very interesting book at the library last Friday. 6. Many houses (to build) in our town every year. 7. This work (to do) tomorrow. 8. This text (to translate) at the last lesson. 9. These trees (to plant) last autumn. 10. Many interesting games always (to play) at our PT lessons. 11. This bone (to give) to my dog tomorrow. 12. We (to invite) to a concert last Saturday. 13. My question (to answer) yesterday. 14. Hockey (to play) in winter. 15. Mushrooms (to gather) in autumn. 16. Many houses (to burn) during the Great Fire of London. 17. His new book (to finish) next year. 18. Flowers (to sell) in shops and in the streets. 19. St. Petersburg (to found) in 1703.

EXERCISE 3. Open the brackets using the correct tense form

1. The porter will (bring, be brought) your luggage to your room. 2. Your luggage will (bring, be brought) up in the lift. 3. You may (leave, be left) your hat and coat in the cloak-room downstairs. 4. They can (leave, be left) the key with the clerk downstairs. 5. From the station they will (take, be taken) straight to the hotel. 6. Tomorrow he will (take, be taken) them to the Russian Museum. 7. At the station they will (meet, be met) by a man from the travel bureau. 8. She will (meet, be met) them in the hall upstairs.

EXERCISE 4 Turn the following into the Passive Voice.

E.g. We often speak about her. — She is often spoken about.

1. We thought about our friend all the time. 2. The doctor will operate on him in a week. 3. The teacher sent for the pupil's parents. 4. They looked for the newspaper everywhere. 5. Nobody slept in the bed. 6. The neighbour asked for the telegram. 7. Everybody listened to the lecturer with great attention. 8. The senior students laughed at the freshman. 9. The group spoke to the headmistress yesterday. 10. The young mothers looked after their babies with great care. 11. Nobody lived in that old house. 12. They sent for Jim and told him to prepare a report on that subject.

EXERCISE 5 Open the brackets using the Passive or Active Voices.

1. Nobody (to see) him yesterday. 2. The telegram (to receive) tomorrow. 3. He (to give) me this book next week. 4. The answer to this question can (to find) in the encyclopedia. 5. We (to show) the historical monuments of the capital to the delegation. 6. You can (to find) interesting information about the life in the USA in this book. 7. Budapest (to divide) by the Danube into two parts: Buda and Pest. 8. Yuri Dolgoruki (to found) Moscow in 1147. 9. Moscow University (to found) by Lomonosov. 10. We (to call) Zhukovski the father of Russian aviation.

EXERCISE 6 Turn the following into the Passive Voice.

I. The students greeted the famous lecturer warmly.2 We asked him about his holidays. 3We received this letter after his departure. 4They often speak about him. . 5I did not leave the window open

EXERCISE 7 Change the following sentences into the Passive Voice.

A using the Indefinite Tenses (give two forms where possible).

Example: Tom gave her a book. — She was given a book. The book was given to her.

1. He broke my watch. 2. The teacher explained the rule to the students. 3. He often asks me to help them. 4. They usually do written exercises in class. 5. She will make a new discovery soon. 6. Steve will make a report at the conference. 7» They play tennis all year round, 8. His friends never forgave his betrayal, 9, The manager offers me several jobs. 10. They will promise you much, but don't imagine they will give you everything. 11. His parents regularly sent him parcels with fruit from their garden. 12. They will give me a leave in July if there is no urgent work. 13. The Spanish government offered Columbus three ships, 14. They usually send their children to camp for summer. 15. The officer charged him with a very important mission, 16, I'm sure we'll settle the matter easily. 17. The policeman fined the driver for exceeding the speed limit 18. Somebody calls her every day. 19. We request the passengers leaving for London to register. 20. The manager will sign contracts tomorrow.

В using the Indefinite Tenses (pay attention to pre­positions),

Example: She looks after him well. — He is well looked after (by her).

1. We sent for the police. 2, They speak much about this book. 3. They often laugh at him. 4. They listened to our conversation very attentively. 5.1 think they will wait for us only in a week. 6. Nobody took notice of his late arrival. 7. We looked through all the advertisements very

attentively. 8, He was a brilliant speaker, and whenever he spoke, the audience listened to him with great attention, 9. They will look after him in hospital much better. 10. Everybody looked at her new dress with interest. 11. She sent them for a taxi. 12. People will talk much about the successful performance of the young actress. 13, They always make fun of him. 14. The teacher pointed out gross mistakes in the translation. 15. He referred to very interesting plans. 16. They agreed upon Monday as the most suitable day. 17. He did not touch upon this question unfortunately. 18. They spoke to him about his promotion yesterday

Lesson 4

ELECTRICITY. ELECTRICAL ENGINEERING

A DIALOGUE

Ann: A distinguishing feature of our time is the unprecedented speed of technology development based upon outstanding scientific achievements.

Pete: Indeed. For thousands of years people led a primitive way of life and then in a comparatively short period of time a gigantic leap has been made in the scientific and technical progress.

Ann; I also thought of how much had been done by the people to reach the present state of the development of human society.

Pete: While the 19th century was mainly the century of steam, the first half of the 20th century was the century of electricity. Now it is increasingly becoming the century of atomic power.

Ann: Yes, Pete, many scientists investigated electric phenomena, and during the 19th century many discoveries about the nature of electricity and of magnetism, which is closely related to electricity, were made. Our life nowadays is revolving around electricity and its many uses.

Pete: Right you are, Ann, we have come to take it for granted. Much had been done by scientists, engineers, workers in producing electricity.

Ann: The present generation knows much about electricity. We now define electricity using the atomic theory. Any matter is made up of atoms. They contain electrons. Their movement in one direction from atom to atom produces electric current.

Pete: It is precisely so. But it is not so simple, as it seems, to generate this current. The common processes of generation of electricity are very uneconomic. To generate electricity it is necessary to get energy and then convert it into electricity.

Ann: And the chief source of energy is heat. So, the common processes of generation of electricity are multistaged ones.

Pete: Yes, Ann. Not direct and with big losses.

Ann: And what about direct methods of electricity generation? Do our scientists work at this problem?

Pete: Yes, they do work. Certain results have already been achieved.

A n n: Do you mean the plasma generator?

Pete: Yes, Ann, I do.

Exercise

Answer the following question. Your answer should contain 10 sentences. ("What had Pete and Ann talked about?") 3. You will find 7 instances of the usage of the -ed forms in the dialogue. Find all of them and define theii functions. They may be used to form the tense and the voice of a verb. They may be used as modifiers.