II. Define clauses in the sentences. Translate them into Ukrainian.

1. When transistors came into use they began to replace vacuum tubes.

2. The problem which is believed to be of great importance for our scientific investigation will be discussed at the conference.

3. This work will be carried out successfully provided you use the data obtained.

4. If you take part in the conference you have to send your report as soon as possible.

5. We obtained good results after the experiments had been made.

6. The electric station was under construction when I came here.

7. Heat would be absorbed until the temperature of the absorbing body attains that of the heat.

8. We asked the student if he had come across any difficulties in his work.

9. She looked as if she were bored to death.

10. The scientist explained that his work is connected with atomic energy.

11. The studies of Venus's atmosphere have shown that it contains too little water vapour and oxygen, but it has a high carbonic content.

12. The smallest particles we see through an electron microscope are much larger than the molecules.

13. In developing countries,which are generally much less equipped,they can store different types of foodstuff together.

14. As soon as the desired amount of CO₂ is reached, atmosphere stabilizing equipment is turned on.

15. As the weight loss is associated with the effective functioning of the refrigerating machine, good insulation is also a factor limiting loss of products.

16. Information about the things people need will help firms to decide what to produce.

17. The project the designer had insisted upon was accepted by the commission.

18. The facts the newspaper referred to were obtained from the interview of the Parliament speaker.

19. It is clear light metals and plastics replace iron and steel in many industries.

20. We know the weather forecasts are based on reports from the weather sputniks.

Read and translate the texts:

CYCLING CONTROLS:

TEMPERATURE ACTUATED CONTROLS.

The controls used to cycle a refrigerating system "on" and "off" are of two principal types: (1) temperature actuated (thermostatic) and (2) pressure actuated.

Temperature Actuated Controls are called thermostats. Whereas float controls are sensitive to and are actuated by changes in liquid level, thermostats are sensitive to and are actuated by changes in temperature. Thermostats are used to control the temperature level of a refrigerated space or product by cycling the compressor (starting and stopping the compressor driving motor) in the same way that float controls are used to control liquid level by cycling the pump (starting and stopping the pump motor).

TEMPERATURE SENSING ELEMENTS.

Two types of elements are commonly used in thermostats to sense and relay temperature changes to the electrical contacts or other actuating mechanisms. One in a fluid-filled tube or bulb which is connected to a bellows or diaphragm and filled with a gas, a liquid, or a saturated mixture of the two (Figs 10.1a and 10.1b). Increasing the temperature of the bulb or tube increases the pressure of the confined fluid which acts through the bellows or diaphragm and a system of levers to close electrical contacts or to actuate other compensating mechanisms (Fig. 10.2). Decreasing the temperature of the tube or bulb will have the opposite effect.

Another and entirely different temperature sensing element is the compound bar commonly called a bimetal element. The compound bar is made of two dissimilar metals (usually Invar and brass or Invar and steel) bonded into a flat strip. Invar is an alloy which has a very low coefficient of expansion, whereas brass and steel have relatively high coefficients of expansions. Since the change in the length of the Invar per degree of temperature change will always be less than that of the brass or steel, increasing the temperature of the bimetal element causes the bimetal to warp in the direction of the Invar (the inactive metal), whereas decreasing the temperature of the bimetal element causes the bimetal to warp in the direction of the brass or steel (the active metal). This change in the configuration of the bimetal element with changes in temperature can be utilized directly or indirectly to open and close electrical contacts or to actuate other compensating mechanisms.

a) b)

Fig. 10.1. Bulb-type temperature Fig. 10.2. Schematic diagram of.

sensing element simplified pressure control.

Exercises:

I. Answer the questions:

1. What is the difference, between temperature actuated controls and temperature sensing elements?

2. What are two types of elements used in thermostats?

3. How do these two types of elements act?