2015-09-07
293
I. Прочтите предложения, укажите в них формы сослагательного наклонения и переведите предложения.
1. It is necessary that the temperature be constant. 2. It is desirable that this device be tested before the experiment.
3. It is required that a spaceship be directed towards the
planet.
4. It is important that any student know the fundamentals
of electrical engineering.
5. If the magnetic circuit consisted of non-magnetic material, the field would be proportional to the current.
6. If the temperature were higher, the results of the test
would be better,
7. If. the tube acted as a simple resistor, the relation between
the plate current and the plate voltage would follow Ohm's Law.
8. Without the radio we would nave very great difficulty
in observing man-made satellites
9. Had the pipe a small cross-section, the water flow per
second would be small.
10.Had a coil more turns, the induced emf would be larger. 11 Were a directional antenna used, the system would operate much better.
12. Were the plates connected together through an external circuit, a current would result and chemical reactions would take place in the cell.
13. If we had used a coil with half the number of turns during our last experiment, we should have got a much lower emf.
14. If we had had more powerful equipment, we should have
carried out our research much earlier.
15. Were there a conducting wire between both points of
unequal potential, the electrons could flow from one of the
points to the other.
16. He suggested that we should use this equipment.
II. Прочтите и переведите предложения, определив тип бессоюзного придаточного предложения:
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1. The experiments showed this substance was unique in its
properties.
2. We know the value of voltage is the same in all the elements of a parallel circuit.
3. The weight of an atom depends on the number of protons
and neutrons it contains.
4. The test we have made is of great importance for our
laboratory.
5. The problem we shall deaf with is connected with new
electronic devices.
6. The devices we are speaking about are constructed on
the basis of photoemission.
7. The computer the engineer is testing was produced in
Minsk.
8. The transmitter we have spoken about is suitable for
this system.
9. We think cadmium is very useful for the application in
transistors.
10. The rays he referred to differ from X-rays.
III. Прочтите слова и группы слов:
(to) rectify [ai], rectifier, rectifying, rectification; characteristic, linear characteristics; symmetrical, symmetrical characteristics; (to) permit, (to) permit easy flow; a surface, on the surface of the contact; some features [i:], some typical features; to oppose, opposing, opposite [zit], the opposite flow; through, through the surfaces, immediate immediately, immediately connected; adjacent, adjacent surfaces, immediately adjacent; ideal, an ideal rectifier; infinite ['infinit], infinite conductance
TEXT
varistors
I. A solid rectifier or diode is a varistor having a volt-current characteristic which is not only non-linear but also non-symmetrical about the origin of currents and voltages.
2. The shape of a rectifier characteristic permits easy flow of current through the device in one direction but presents high resistance to current flow in the opposite direction. 3. The device we are speaking about is called a non-symmetrical varis-tor.4. A semiconductor contact rectifier, whatever its size, or electrical properties, consists of a layer of the semiconductor material with two metal contacts on its surface or surfaces. 5. If both of these contacts were rectifying, then the device would really be a series combination of two rectifiers in series opposing.6. In order to use the properties of the device in the best way, it is necessary that the rectification at one of these contacts be as ideal as possible. 7. It is also necessary that the •rectification at the other contact would be eliminated at the same time.
8. This can be done through the proper choice of a nonrectifying metal for the second contact or through suitable rectification-destroying treatment of the semiconductor surface before applying the contact metal. 9.The place of the rectification at the non-ohmic contact is often called the barrier layer or blocking layer l0. It consists of a very thin layer of semiconductor, immediately adjacent to the metal contact in which the local resistivity is many times greater than in the bulk material. II. The magnitude of the local resistivity, as well as the thickness of the layer itself, depends upon the direction and the magnitude of the voltage applied across the contact. 12. Typical barrier layer thickness runs from 10-6 to 10-3 cm. 13. The primary function of a rectifier is to serve as one-way valve allowing current to flow easily in one direction and only with great difficulty in the other. 14. The ideal rectifier would of course present infinite conductance in one direction and infinite resistance in the other.
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15. Rectifying devices of various kinds using contacts between metals and semiconductors approach this ideal with certain characteristic features which are more or less common to all such devices.
16. The features we have just mentioned above must be discussed in details if one wants to understand the operation of these devices much better.
Слова для запоминания
п feature, origin, rectifier, surface, thickness, treatment
v destroy, mention, permit, rectify, serve
a adjacent, local, solid
adv immediately
prep as well as
Слова для повторения
n layer, magnitude, shape
v allow, approach, eliminate, present, run (ran, run)
a opposite, thin
