河南理工大学毕业设计（论文）附录1. Energy conversion and conservationThe conversion of mechanical energy to heat is by no means new to us. We are also familiar with other transformations of energy. Chemical energy is converted into heat when fuel burns. Electrical energy is transformed into heat and light in electrical lamps and electrical stoves. Radiant energy turns into heat when sunlight strikes an object which absorbs it. “All contradictory things are interconnected; not only do they coexist in a single entity in given conditions, but in other given conditions, they also transform themselves into each other.” In a word, all energies maybe converted from one form to another and what is more, they all can transform into heat by themselves. Heat is an energy of irregular motion of particles in a substance, at ordinary temperature it is less unable than any of the other energies.However, at high temperatures heat energy may be converted into energy of more usable forms. Some people have made different kinds of machines to convert heat into mechanical energy. Diesel and gasoline engines are designed to convert heat that is developed by the burning of fuel into mechanical energy for running tractors, trucks, and cars. The mechanical energy transformed from heat in a steam turbine is made to operate generators. And the generators, in turn, convert the mechanical energy. All these transformations are taking place every minute and everywhere in our daily life and production. In any energy transformation, there is some loss, but no energy is destroyed. The part that is lost is simply wasted. If all of the energies that are wasted were added to that used, the total would be found to be equal to the total supplied. The form may be changed, but the amount remains unchanged. The fact that energy can be changed from one form to another, but can neither be created nor destroyed, constitutes one of the most important laws in science, the law of conservation of energy. No one form of energy can be long conserved, but the total is conserved at any time. A machine may be designed to lift a much larger weight than the force that is applied, but it can never produce more work than was supplied to it. In other words, a machine cannot have an efficiency greater than one. Since man cannot create or destroyed energy, he must use the energy that is available to him.Some devices were designed for the purpose of doing work without the need of supplying energy. These are the so-called perpetual-motion machines. We say that such machines are impossible because they violate the law of conservation of energy. The attempt has never been successful. And it will never be successful.2. Generator and electricity (1) Faraday and his GeneratorThe electric current in our homes is produced in power stations which usually contain several generators. These are machines which generate electric current when they are turned. So there has to be some kind of engine to turn them.What kind of engine can we use? Steam engines are suitable, and so are oil engines. Sometimes the water of a great river can turn the generators, and so power stations are often built near dams.The water which is stored behind a dam flows out with great force when it is allowed to do so. We can use this force to turn machines which are called turbines. The water is led through big pipes to the turbines, and then they turn the generators. These supply the country with useful current.Michael Faraday (1791-1867) made the first generator. He was a great scientist. He studied gases and changed some of them into liquids. He made many discoveries in chemistry and electricity. Before his time scientists got their electric current from electric cells. Several cells together form a battery. An Italian, Volta, made the first battery and it produced a small current. Modern cells are boxes which contain acids and other materials such as metals or carbon rods. Faraday knew about Voltas work, but he wanted to produce an electric current by using magnets.An electric current which flows through a coil of wire round an iron rod produces magnetism in it. Faraday wanted to do the opposite: he wanted to produce a current in a wire by using magnetism. He tried to do this for a long time, but he failed completely until he moved a wire near the magnets. Then his instruments showed that a small current was flowing in the wire. Either the magnet or the wire had to move. He made a small machine to turn a coil of wire near the magnets, and this generated a current. It was the first generator in the world. All modern generators depend on Faradays work. The magnets in them are usually electromagnets; even in an electromagnet a little magnetism remains in the iron after the current is switched off. As soon as the generator turns, a small current appears. This increases the magnetism, and so the current increases. This again increases the magnetism, and so on. In a few seconds there is qui