Essay Example on Natural Processes are Characterized by Direction and Irreversibility








Natural processes are characterized by direction and irreversibility however in most of the laws described in this book this is not reflected at least explicit To break eggs and make fried eggs is not difficult to recreate the same raw eggs from the finished fried eggs it is impossible The smell of an open bottle of perfume fills the room but you can not assemble it back into the bottle And the reason for such irreversibility of the processes taking place in the Universe lies in the second law of thermodynamics which for all its seeming simplicity is one of the most difficult and often misunderstood laws of classical physics First of all this law has at least three equal rights proposed in different years by physicists of different generations It may seem that there is nothing in common between them but they are all logically equivalent to each other From any formulation of the second principle two others are mathematically deduced We begin with the first formulation which belongs to the German physicist Rudolph Clausius see Clapeyron Clausius equation Here is a simple and clear illustration of this formulation we take from the refrigerator an ice cube and put it in the sink After some time the ice cube will melt because the warmth of the warmer body air will be transmitted to the colder ice cube From the point of view of the law of conservation of energy there is no reason for thermal energy to be transmitted in this direction even if the ice become colder and the air was warmer the law of conservation of energy would still be fulfilled The fact that this does not happen just shows the already mentioned direction of physical processes

Why this is how ice and air interact we can easily explain by considering this interaction at the molecular level From molecular kinetic theory we know that the temperature reflects the speed of movement of body molecules the faster they move the higher the body temperature This means that air molecules move faster than water molecules in an ice cube When the air molecule collides with the water molecule on the ice surface as experience tells us the fast molecules on average slow down and the slow ones accelerate Thus water molecules start moving faster or which is the same thing the temperature of the ice rises This is what we mean when we say that heat is transferred from the air to the ice And within the framework of this model the first formulation of the second law of thermodynamics logically follows from the behavior of molecules When you move a body to any distance under the action of a certain force work is done and various forms of energy just express the ability of the system to do certain work Since heat which reflects the kinetic energy of molecules is a form of energy it can also be converted into work But again we are dealing with a directed process You can translate work into heat with one hundred percent efficiency you do this every time you press the brake pedal in your car all the kinetic energy of your car's movement plus the energy of the pedal force you expended through the work of your foot and the hydraulic brake system is completely converted into heat stands out in the process of friction pads on the brake discs

The second formulation of the second law of thermodynamics states that the reverse process is impossible No matter how much you try to turn all the heat energy into work heat losses to the environment are inevitable It is not difficult to illustrate the second formulation in action Imagine the cylinder of the internal combustion engine of your car It injects a high octane fuel mixture which is compressed by a piston to high pressure after which it ignites in a small gap between the cylinder head and a freely moving piston densely attached to the cylinder walls When explosive combustion of a mixture a significant amount of heat is released in the form of incandescent and expanding combustion products the pressure of which pushes the piston downward In an ideal world we could achieve the efficiency of using the released thermal energy at 100 completely translating it into the mechanical work of the piston In the real world, no one will ever assemble such an ideal engine for two reasons First the walls of the cylinder inevitably heat up as a result of the combustion of the working mixture part of the heat is lost idle and drained through the cooling system into the environment Second part of the work inevitably goes to overcome the frictional force as a result of which the walls of the cylinders are heated another heat loss even with the best motor oil Thirdly the cylinder needs to return to the initial compression point and this is also a work to overcome the friction with the release of heat spent idle As a result we have what we have, namely the perfect thermal engines operate with an efficiency of not more than 50

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