4. Translate the following sentences paying attention to modal verbs with Perfect Infinitive:

1. Why have you made this mistake? You must have known the rule. 2. Dr. Smith hasn’t arrived yet. He must have missed his bus. 3. I could have gone to the conference, but I lost my invitation. 4. The explosion must have occurred long ago. 5. No living being could have survived in such a climate. 6. Some problems of science could not have been solved without isotopes. 7. The engineer might have overlooked something that may turn out to be important in carrying out this experiment. 8. All the preparations must have been completed long ago. 9. He may have got the condenser he needed for his experiment. 10. He cannot have broken the tube while making this experiment. 11. You should have changed the current strength at all points of the circuit. 12. He may have got the article he needed. 13. You should have helped your friend. 14. It is believed that these rocks could not have been more than 5 000 years old. 15. Life may have existed on that planet. 16. You might have made the experiment more carefully.

5. Translate the following sentences. Pay attention to the form of the infinitive.

1. It was found that under certain conditions the electrons may be made to obtain enough energy to overcome the surface restraint.

2. Currents of electricity can be produced by certain chemical actions.

3. If necessary, AC can be transformed to the D.C. form for actual use.

4. It is easy to transform AC power from one voltage to another by means of the transformer, but this operation cannot be done with the DC power.

5. The cathode of an electronic tube may be made in the form of a filament of a high resistance material.

6. The element should be made of a material that is a poor emitter of electrons.

7. They must be used to transform light and heat energy directly into electric energy.

8. It should be remembered that an electron, being negatively charged, will move towards the other end of the circuit, called "positive".

9. If the system is to serve as a voltmeter, a resistor has to be added in series.

10. To obtain the above results the diameter of the wire must be changed.

11. The instrument may have been improved, because it became more accurate.

VI. Nouns as Attributes

1. Translate the following sentences. Pay attention to the underlined attributive word-combinations.

An oscillating current varies periodically at a frequency determined by the circuit constants.

To achieve reliability individual circuit bricks are used.

The computer variables may be displacements, velocities, accelerations, pressures, temperatures, or angles.

4. The Russian text is printed out on a paper tape.

Conduction takes place due to generation of electron-hole pairs by thermal energy.

6. Here we see the temperature dependence of resistance of 3 samples of germanium over a wide temperature range.

7. The ordinary method of producing high-frequency waves is by means of vacuum tubes.

8. The thermionic tube is finding an important place in the power field, as a rectifier, leading to the development of direct-current power transmission systems and of direct-current excitation apparatus to replace the rotating machines.

9. The armature magnet conductors are laid in slots cut in the iron core parallel to the shaft.

10. Each end of an armature coil is connected to an insulated copper segment that is part of a cylindrical group.

11. The series motor field must carry the full armature current.

12. It should be noted, that mercury-arc rectifiers and electronic devices may make DC. high-voltage transmission popular.

13. Switches of this kind are classified under a general term of safety-type switches or simply safety switches.