Varieties of energy (a)

There exist many sources of energy in the world both potential and kinetic. One source consists in water falling from a high level Such as an upland lake. Another source is wind or moving air. Others consist in tides in the sea, heat from subterranean sources and lastly coal deposits and oil wells yielding mineral oil. kind. Moreover some stores of energy such as coal and oil can never be replaced by us when once used up. On the other hand stores of high level water are con inually being replaced by rain and wind and tides will not, as far as we know, ever cease to exist. Hence a very important matter is the conversion of energy from one form to another. The form most required by us is mechanical, rotational energy.

This energy is required to rotate shafts in a factory for driving various machines and also for driving the wheels of vehicles of automobiles or locomo­tives. The energy of water power is very unequally distributed, some countries such as Norway and Switzerland being rich in it and some such as England poor. England is rich in the potential energy of coal but has little oil wells.

Appliances for converting energy from one form to another are called engines. Thus a heat engine is a machine for converting heat energy into mechanical energy of rotation by the combustion of coal or oil and a turbine or water engine can convert the kinetic energy of falling water into mechanical rotational energy.

The efficiency of an engine is the ratio of the energy delivered in the desired form to that given to the engine in the available form. Thus having given a heat engine much energy by combusting coal or oil we take from it mechanical energy in kinetic form, rotational or motional.

Ex 1. Point out which of these sentences contains the information from the text (A):

1. This science deals with the rates of reactions and the methods of accelerating them.

2. The potential energy of the weight in its highest position is the same as its kinetic energy after it has fallen to its lowest position.

3. All sources of energy are not equally useful to mankind hence a very important matter is the conversion of energy from one form to another.

Ex. 2. Rearrange the sentences to make a summary of the text, use 'since' (так как) wherever possible;

1. These sources of energy are not equally useful to mankind.

2. There exist many sources of energy in the world both potential and kinetic, such as wind, moving air or water falling from a high level.

3. The conversion of energy from one form to another is a very important matter as the form most required by us is mechanical rotational energy.

4. The ratio of the energy delivered in the desired form to that given to the engine is the efficiency of an engine.

5. Appliences for converting energy from one form to another are called engines.

The end of the universe (b)

We know that energy cannot be created or destroyed. This law of conservation of energy is also referred to as the first law of thermodynamics. Thermodynamics is the branch of physics, which deals with the conversion of mechanical energy into thermal energy and the reverse process.

Although energy is always conserved, it usually winds up as heat energy. For example, if you rub your hands together, they will get warm. Your| muscle energy has changed to heat energy. Energy continually runs downhill from a higher to a lower grade. This is called the second law of thermodynamics.

So the second law of thermodynamics is essentially the law of degrada­tion of energy. A general statement of this law: "No change in a system of bodies) that taks place of itself can increase the available energy of the system". Any actual physical process is accompanied by frictional effect and] therefore is irreversible. Or in the ojher words a strictly reversible frictionless process being an ideal, it may be approached but never attained. We should never assume that we have an inexhaustible supply of energy. We constantly need more energy because whenever we use energy, we de-1 grade that energy into some less useful form. Heat energy is a lower form of energy due to the fact that it cannot readily be transformed into useful work. One sign of me degrading of energy is that heat always flows from a I warmer object to a cooler one; it never does die reverse. If you put an ice cube in a hot drink, heat flows from the hot liquid to warm and melt the cube. Heat energy never flows from cold object to a hot one, making the cold object colder and me hot object hotter.

The lower the temperature of an object, the lower the grade of energy it contains.

The downgrading of energy is manifested in another way. Natural processes tend to proceed toward a state of greater disorder. Nothing goes from disorder to order. Opening a bottle of perfume, you let the molecules of perfume rush out into the air in disorderly fashion. They never go back into the bottle and return to an orderly state! Similarly, shaking some salt and pepper together, you mix them. There is no way you could mix, stir, or shake the mixture to extract the salt from the pepper and restore two orderly piles of distinct substances. The disorder of the universe continually increases.

In case this condition exists everywhere, the natural outcome will be that everything in the universe will degenerate into an end. This running down of energy is referred to as "entropy" or the "heat-death" of the universe. However, you don't need to worry about it, unless you plan to be around in a billion years or so.

Ex. 1. Find the equivalents:

phenomenon of friction

reverse process

irreversible process

reversible process

quantity of heat generated

available energy of the system

change of state of the system

ideal frictionless process

any actual physical process

first and second laws

of thermodynamics

-обратный процесс

-обратимый процесс

-первое и второе начала термодинамики

-идеальный процесс, в котором отсутствует трение

-явление трения

-необратимый процесс любой действительный физический процесс

-имеющаяся энергия системы любое преобразование любое, превращение энергии из одной формы в другую

-изменения состояния системы

-количество полученной теплоты