Radioactive changes, occuring in the nuclei of atoms, are not affected by ordinarily used chemical processes. 7. Electrical energy being released, a force called electromotive force (e. m. f.) is developed. 8. One coulomb passing a point in a circuit per second, the current strength is 1 ampere. 9. Pure water, rubber, and glass are insulators; impure water containing dissolved acids, salts, or bases, is intermediate in conductivity.
Задания к тексту A
. I. Прослушайте текст смысловые группы в каждом предложении абзаца 1. Прочтите абзац за диктором.
II. Прочтите и переведите текст А.
Microscopic and Macroscopic Manifestation of Charge
1. Now we know electrical force to be the ruling interaction over a wide domain of nature from the size of atoms to the size of man.
2. Now we know that the simplest atom, an atom of hydrogen, consists of one proton and one electron. These two constituents of the atom are helt together by their force of mutual electrical attraction. Because of the laws of quantum mechanics, these two particles do not draw together into the same spot. Instead the light-weight elec-
tron takes for its domain of motion a spherical region of space, centered at the heavier proton. The average separation of the two particles is about 0.5 Angstrom (0.5xl0~8 cm). Under certain conditions, the electron may temporarily have some extra energy and extend its motion to greater distance, but the diameter of the atoms can never be less than about 1 Angstrom. If sufficient extra energy is given to the electron, it may escap-e the attractive force of the proton altogether and move away to a great distance. In this case the atom is said to be "ionized"; the proton left behind is called a positive ion. For this proton the symbol H+ is sometimes used, designating a positively charged hydrogen atom. Under conditions of extreme temperature, above several thousand degrees Kelvin, hydrogen gas may be largely "ionized", consisting mostly of free protons and electrons. Such a gas is called a plasma.
3. In a plasma electrical forces reach out to relatively great distance, and each ion "feels" the presence of many other ions. At more moderate temperatures, however, each electron will be attached to its own proton, forming a neutral hydrogen atom, designated simply HL Because electron and proton have equal and opposite charge, the atom as a whole is neutral and its electrical effects do not extend very far beyond its own boundaries. A gas of ordinary atoms is called a neutral gas, because each atom as a whole is neutral.
4. One might think that in a neutral gas, electrical* force has been confined entirely within the atom and is of no consequence outside it. This is not true. Rather the neutrality of the atom has sharply limited the range of the force. If two hydrogen atoms get quite close together, for example, to a separation of their centers of one Angstrom, they are in contact, or touching. They a*e so close together that the proton and electron of one atom can separately feel the electrical forces of the proton and electron of the other atom. The net force felt by the atom is not a Coulomb force, that is it does not vary inversely with the square of the distance of separation. It is considerably more complicated, its exact form depending on the laws of quantum mechanics as well as on the presence of electrical forces. At great separation there is no force at all. As the atoms approach one another, they experience a weak attractive force, but when they
get so close together that they are "touching", this changes to a strong repulsive force that does not allow the two atoms to overlap significantly.
5. The weak attraction is not unimportant2. It causes pairs of hydrogen atoms to join together to form hydrogen molecules (H2). The still weaker but analogous force attracting hydrogen molecules4 to one another is responsible for the condensation of hydrogen gas to a liquid at low temperature, and the freezing of hydrogen into a solid at still lower temperature.
Notes to the Text
1. one might think ... —можно было бы подумать..;
2. the weak attraction is not unimportant — зд. нельзя сказать, что слабое притяжение не имеет значения.
I. Дайте русские эквиваленты.
Constituents of the atom; the same spot; domain of motion; some extra energy; to extend the motion; sufficient energy given to the electron; to escape the attractive force; the proton left behind; the symbol H designating a positively charged hydrogen atom; extreme temperatures; largely "ionized"; attached to its own proton; far beyond its own boundaries; confined entirely within the atom; of no consequence; the range of the force; the net force; vary inversely with the square of the distance; no force at all; still lower temperature.
П. Дайте английские эквиваленты.
Взаимное электрическое притяжение; законы квантовой механики; при определенных условиях; достаточная энергия; в этом случае; говорят, что атом «ионизируется»; относительно большое расстояние; состоящий главным образом из свободных протонов и электронов; при более умеренных температурах; равный и противоположный заряд; атом в целом; обычный атом; точная форма; наличие электрических сил; пары атомов водорода; сила, притягивающая молекулы водорода; замерзание водорода.
III. Ответьте на вопросы по тексту А.
1. By what force are the two constituents of the atom held together
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