3. Переведите предложения, определяя, какой частью речи является ing-форма: герундием, отглагольным существитель­ным или причастием.

A

1. Every new idea is immediately taken up and developed further, forming the initial point of an avalanche-like process. 2. It has been shown that there is a distortion of the crystal lattice, accompanying the charge-ordered state. 3. What is worth doing is worth doing well. 4. At this stage innovation becomes a group and not an individual activity, involving both a sophisticated body of information and a sophisticated technology. 5. Soon Pierre Curie joined Marie Curie in her search for the "mysterious" substance, giving up his own research. 6. It is no good stressing a paradox if your wish to excite curiosity of the audience unprepared for the lecture. 7. In 1913 Bohr proposed the solar theory of the atom, giving rise to still greater activity in both theoretical and experimental nuclear physics. 8. The editor could not help detecting many errors both of fact and of thinking. 8. Are these prognoses really worth making? 10. To find out more about the space scientists sent little moons, or satellites, circling in orbits above the Earth. 11. Space research requires solving many problems. 12. Defects in the system delayed launching the missile.

B

1. Everything must have a beginning. 2. The proof of the pudding is in eating. 3. Wisdom denotes the pursuing of the best end by the best means (F. Hutcheson). 4. Swallow all your learning in the morning, but digest it in company in the evening. (Ph. Chesterfield). 5. By that definition we mean the following. 6. We obtained these values in terms of the following formula. 7. The problem, however, is in not dividing the structure finely enough. 8. Before starting the engine it is necessary to test the piping for leakage (утечка). 9. The boy playing in the garden is my son. 10. Fortran became a widely accepted programming language for the coding of mathematical applications. 11. The matters related to machine ratings, insulation, and allowable temperature rise, as well as the determination of losses, are subjects of standardization by professional organizations. 12. Losses are on inevitable part of any energy-transforming device. 13. The efficiency of electric machine is most commonly determined by the measurement of losses instead of by directly measuring the input and output under load conditions. 14. Many of the definitions and methods of measuring losses and of specifying effi­ciencies as well as other performance characteristics are standardized by vari­ous national and international professional agencies. 15. Besides affecting the efficiency and hence the operating cost of the ma­chine, the losses determine the heating of the machine and consequently the rat­ing of power output that can be obtained from a machine without overheating and causing deterioration of insulation over a reasonable period. 16. Also, the cur­rent components for supplying the losses and the associated voltage drops af­fect regulation and other performance characteristics of a machine. 17. The effect of the brush-contact resistance in dc machines is conventionally taken into account by assuming a full-load drop of 2 volts in series with the armature circuit.

Homereading. DC Machines. The Danish scientist, Oersted, discovered how to obtain an emf by ROTATING a LOOP of wire in a MAGNETIC FIELD. This device became known as the GENERATOR, a relatively simple machine with just four major parts-STATOR, ARMATURE, SLIP RINGS, AND BRUSHES. The generator is a device used to change MECHANICAL ENERGY into electricity. PART OF A DIRECT CURRENT GENERATOR If you make a slight change in the slip rings of an a.c. generator, you can obtain direct current instead of alternating current. Figure 1.-Parts of a d.c. generator. In figure 1, the two slip rings have been Changed to a SINGLE, TWO-SEGMENT RING. The BLACK leg of the loop is connected to the BLACK SEGMENT, and the WHITE LEG to the WHITE segment. The two segments are insulated from each other, so that no electrical contact is possible. The SPLIT RING is known as the COMMUTATOR. The two BRUSHES are on opposite SIDES of the SPLIT RING, mounted in such a manner that each brush is in contact with only one segment at a time. HOW A DIRECT CURRENT GENERATOR WORKS The generation of the emf by the loop cutting across the magnetic field is the same in a d.c. as it is in an a.c. generator. The change to d.c. takes place at the COMMUTATOR. Figure 2.-Operation of a d.c. generator. The loop in figure 2A is moving in a counterclockwise direction, parallel to the flux. Hence, no emf is generated. Notice that the BLACK BRUSH is just coming in contact with the BLACK segment, and the WHITE BRUSH with the WHITE segment. In position B, the flux is being cut at a maximum rate. The BLACK BRUSH is contacting the BLACK SEGMENT and the WHITE BRUSH the WHITE SEGMENT. And the galvanometer needle is deflected to the RIGHT. At position C, the loop has completed 180° of rotation. No flux is being cut, so the emf is zero. The important thing to observe in position C is the action of the segments and brushes. The BLACK BRUSH is SLIPPING off the black segment and ON TO the WHITE. At the same instant, the WHITE BRUSH is leaving the WHITE segment, and going on to the BLACK. The SWITCHING of commutator segments also switches legs of the loop. In this way the BLACK BRUSH is ALWAYS in contact with the leg moving DOWNWARD, and the WHITE brush in contact with the leg moving UPWARD. While the current is actually reversed in the loop it is ALWAYS FLOWING in the same direction through the galvanometer. A graph for one cycle of a d.c. generator is given in figure 3. The generation of the emf for positions A, B, Figure 3.-Graph of a d.c. voltage. and C is the same as for an a.c. generator. But at position C, the brushes, in moving from one commutator segment to the other, cause the current to flow in the positive direction rather than becoming negative. The d.c. furnished by a single loop armature is very bumpy. It starts at zero, rises to maximum, and falls back to zero TWICE for each rotation of the loop. To produce a smoother d.c., more loops of wire are added to the armature. In figure 4, two coils are used instead of one. There are now four segments but only two brushes in the commutator. With this arrangement, the voltage cannot fall any lower than point A, so the bump in the voltage Figure 4.-Voltage from a two-coil armature. (ripple) is limited to the rise and fall between points A and B. By adding still more armature coils, the voltage ripple can be further reduced. MECHANICAL ENERGY FROM ELECTRICITY In the last chapter, the generator was described as a device used to change MECHANICAL ENERGY into electricity. In this chapter, the motor is described as a mechanism that changes the ELECTRICITY back into MECHANICAL ENERGY. Radiomen do not have many contacts with motors, other than by pressing a button to start or stop them. But every man in the radio rates should know and understand the principles of electric motors. The MOTOR-GENERATOR sets that power the large transmitters use an ELECTRIC MOTOR to drive one or two GENERATORS, depending upon the model of transmitter. The motors take their power from the 110-, 220-, or 440- volt ship's supply, and the GENERATOR delivers several voltages-both a.c. and d.c.-to the transmitter. Your ship's real source of power is the oil in the tanks.

In the boilers, burning oil changes water to steam. The steam drives a turbine, and the turbine turns the ship's generators. The emf from the generators runs the motor of the transmitter's MOTOR-GENERATOR set-and the generator changes the motor's MECHANICAL energy back into the ELECTRICAL energy to operate the transmitter.

Figure 5.-Action of a conductor in a magnetic field.
The ACTION of a motor is based upon the old, familiar law-UNLIKE POLES ATTRACT, and LIKE POLES REPEL. To review the laws, look at figure 5. A conductor is hung in a position that will permit it to swing freely either in or out of the horse shoe magnet. Two dry cells are connected to the wire through a double-pole, double-throw switch. The switch is so connected that by throwing the switch from one set of contacts to the other the current through the conductor is reversed. Closing the switch in one direction causes the CONDUCTOR to move INTO the magnet. And throwing the switch in the opposite direction causes the conductor to move OUT.
The conductor's movement is caused by the COMBINED ACTION of TWO MAGNETIC FIELDS-the field around the conductor and the field of the horse shoe magnet.

Figure 6.-Motor action.
In the bottom drawing of figure 6A, the conductor's field and the flux of the field coil combine to CANCEL each other at the BOTTOM and ADD to each other at the TOP. This leaves a GREATER FORCE tending to move the conductor DOWN than up-and the conductor will move DOWN. In figure 6B, the current is flowing in the opposite direction, and the effect of the field is reversed. The two fields CANCEL ON TOP and ADD on the bottom, so the conductor moves UP.
The action of a conductor in a magnetic field is known by many different names, but the term "motor action" is as good as any. PARTS OF D.C. MOTOR The essential parts of a d.c. motor are similar to those of a generator. Look at figure 7. The four main parts are-STATOR, ARMATURE, COMMUTATOR, and BRUSHES. A battery attached to the brushes provides the energy to drive the motor. The differences between a d.c. motor and a generator are usually only in the manner of mounting the brushes and connecting the windings. Actually, some d.c. motors may be used as d.c. generators without any change at all.

Figure 7.-Parts of an electric motor.
segment to the other, and the direction of the current in the loop will be reversed. The black leg will now move UP and the white leg DOWN.

Compare the structure and function of a generator to an electric motor

Electric motors and generators have several structural features in common. Each consists of a stator that provides a magnetic field and a rotor that rotates within the magnetic field. In both motors and generators the magnetic field may be supplied either by permanent magnets or by electromagnets. The rotor in both an electric motor and a generator consists of coils of wire wound on a laminated iron armature and connected through brushes to an external circuit.

An electric motor and a DC generator are similar in that their rotor coils are connected to the external circuit through a split-ring commutator. An AC generator is different as its rotor coils are connected to the external circuit through slip rings. An AC induction motor is different from a generator as its rotor coils are not connected to an external circuit and its field is always supplied by electromagnets.

The function of an electric motor is the reverse of the function of a generator. An electric motor converts electrical energy into mechanical (usually rotational) energy. A generator converts mechanical (usually rotational) energy into electrical energy. A motor rotates when current is supplied while a generator supplies current when rotor is made to rotate. It is possible to have a DC motor act as a generator by providing the energy to rotate the armature containing the coils.