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III. Writing Section

1. Translate the following text from English into Russian. Use a dictionary if necessary.

Concept of Internal Energy

1. The molecules of a body possess kinetic and potential energy. Atoms inside a molecule and electrons inside an atom also possess kinetic and potential energy. The sum of the kinetic and potential energies of all particles of which a body consists is called internal energy of that body.

2. Experiments have shown that the internal energy of bodies is determined by their state. When external influences are absent its internal energy remains constant. So, internal energy is a function of state.

3. There is a constant energy exchange between individual parts of a body. For many years scientists have studied transformations of energy and have come to the conclusion that energy is never made and never destroyed. Whenever one kind of energy appears, an equal amount of some other kind of energy disappears.

4. Molecular physics deals only with phenomena in which molecules remain unchanged. In such phenomena all variations of the internal energy of a body are due to the variations of the kinetic and potential energies of its molecules. In short the term internal energy of a body is the sum of the molecular-kinetic and molecular-potential energies of the body.

5. An ideal gas has no molecular potential energy as there are no forces of interaction between its molecules. Besides, the atoms of an ideal gas are particles and they have no internal structure. They have no energy due to the motion and interaction of particles making them up. Hence, internal energy of an ideal gases the sum of the values of kinetic energy of random motion of all molecules.

6. At this stage the question arises: what energy is not a part of internal energy of a body? Let us use the Earth as an example of such a body. The Sun attracts the Earth and the Earth moves in an orbit around the Sun. It means that it possesses both potential and kinetic energy with respect to the Sun. This energy is not a part of the internal energy of the Earth. Hence the internal energy of a body does not include kinetic and potential energy of that body with respect to all external bodies. In the same way the internal energy of a system of bodies does not include kinetic and potential energy of this system with respect to bodies that are not a part of this system.

His Revenge

Niels Bohr (1885-1962), the famous Danish physicist, discovered many important laws concerning the structure of atomic nucleus. He always worked hard. But once it so happened that he had not prepared for his seminar at the university. His report was very bad and the teacher was surprised.

Bohr, however, did not lose the presence of mind¹ and finishing his report said in conclusion:

“I have listened here to so many bad reports that I ask you to regard this one as my revenge.”²

¹ to lose the presence of mind – терять присутствие духа

² to regard as revenge – считать местью

Дата добавления: 2015-05-31