IV. Напишите 2-е, 4-е, 5-е предложения упражнения III в прошедшем и будущем времени (со сказуемым в пассивной форме).
Образец. 1. A new source of power is required. – New sources are required.
2. A new source of power was required. – New sources were required.
3. A new source of power will be required. – New sources will be required.
V. Выберите правильный ответ на вопрос.
1. What do portable radios and flash-lights use as their source of power? (generators, batteries)
2. What current is drawn from the battery? (small, large)
3. What machines can supply large amounts of power? (devices, generators)
4. What is called "armature"? (the loop of wire which rotates through the field, the sides of the loop)
VI. Дайте краткие ответы на вопросы диалога.
1. Does a portable radio require little current? – Да.
2. What is the source of little current? – Батарея.
3. And what currents do heavy motors require? – Большие токи.
4. What machines can supply larger currents? – Генераторы.
VII. Посмотрите текст и, употребив данные слова, расскажите о:
– источнике энергии – batteries, generators, power, current, devices, motors, some kinds of, flash-lights, portable radio, electrical equipment, amount, use, require, supply, there are, large, small, heavy, some, such as;
– устройстве и работе элементарного генератора – loop of wire, (uniform) magnetic field, induced current, armature, slip rings, sides of the loop, e.m.f., consists of, rotates, causes, connect to, is called, rotate with, cut through, is induced.
Text 2
Elementary Generator Operation
Here is the way the elementary generator works. Assume that the armature loop is rotating in a clockwise direction, and that its initial position is at A (nought degrees). At position A, the loop is perpendicular to the magnetic field, and the black and white conductors of the loop are moving parallel to a magnetic field. If a conductor is moving parallel to a magnetic field, it does not cut through any lines of force, and no e.m.f. is generated in the conductor. This applies to the conductors of the loop at the instant they go through position A – no e.m.f. is induced in them, and therefore no current flows through the circuit. The ammeter registers zero.
As the loop rotates from position A to position B, the conductors are cutting through more and more lines of force, until at 90 degrees (position B) they are cutting through a maximum number of lines of force. In other words, between 0 and 90 degrees the induced e.m.f. in the conductors builds up from zero to a maximum value.
|
|
|
As the loop continues rotating from position B (90 degrees) to position C (180 degrees) the conductors which are cutting through a maximum number of lines of force at position B begin to cut through fewer and fewer lines until at position C they are moving parallel to the magnetic field and no longer cut through any lines of force. The induced e.m.f. will therefore decrease as the loop moves from 90 to 180 degrees; and the current flow will also vary as the voltage varies.
From 0 to 180 degrees the conductors of the loop have been moving in the same direction through the magnetic field, and the polarity of the induced e.m.f. has therefore remained the same. As the loop starts rotating beyond 180 degrees back to position A, however, the direction of the cutting action of the conductors through the magnetic field reverses. As a result, the polarity of the induced e.m.f., and the current flow will reverse.
Words and Word Combinations
| way n | способ |
| assume v | предполагать, допускать |
| in a clockwise direction | по часовой стрелке |
| initial a | начальный |
| nought n | ноль |
| lines of force | силовые линии |
| apply to v | относиться к |
| at the instant | в момент |
| register v | показывать |
| until cj | пока не |
| in other words | другими словами, иначе |
| number n | количество, число |
| build up v | поднимать(ся) |
| value n | величина |
| no longer cut | больше не пересекают |
| decrease v | уменьшать(ся) |
| vary v | изменять(ся) |
| beyond prep | за |
| remain v | оставаться |
| however cj | однако |
| reverse v | изменять(ся) |
|
|
|
E x e r c i s e s
I . Прочитайте и переведите слова и словосочетания.
1) current flow, generator operation, action, initial position, direction, lines of force, magnetic field, maximum value (number), assume, clockwise, registers, builds up, remains, continues;
2) conductors moving parallel to, conductors cutting through more and more lines of force, conductors moving in the same direction.
Дата добавления: 2019-11-16; просмотров: 209; Мы поможем в написании вашей работы! |
Мы поможем в написании ваших работ!