Basic-Gyan

The Clausius inequality is a consequence of the second law of thermodynamics. Clausius inequality is related to the entropy of thermodynamics system. It is also known as " Clausius Theorem ". While entropy is defined as a measure of the randomness or disorder of a thermodynamic system . Clausius Inequality It states that- " In a cyclic operation, the sum of the 'dQ/T' term over a complete cycle (or cyclic integration of the 'dQ/T' term) is less than or equal to zero, depending on whether the process or a cycle is reversible or irreversible ". Thus; Where,         dQ is the amount of heat added to the                   system at any point          T is the temperature at this point The above equation is known as the Clausius inequality and it suggests to us the criteria for reversibility and irreversibility of the thermodynamic cycle; ➛ The Clausius inequality is valid for all the cycles whether it ...

A perfect thermometer would show an equal amount of temperature difference for equal amount of heat transfer for all the substances, but this was impossible because the specific heat of all the substances is different.         Before the invention of absolute temperature scale, the temperature was measured mostly by air or gas thermometers because the difference in readings of temperature in gas thermometers at different pressures was in-appreciably small (which was not possible for mercury and alcohol thermometers). This temperature scale was relative as it was dependent on the property (specific heat) of the substances.              William Thomson thought of developing an absolute temperature scale which would be independent of the specific heat of the substance so that any substance used in the thermometer should show the same temperature difference for the same amount of heat transfer. This was the purpose of developing an abso...

There are two most popular statements of second law of thermodynamics i.e. Kelvin-plank statement and Clausius statement. KELVIN-PLANKS STATEMENT It is impossible to make an engine (operating in a cycle) which works on the single temperature source and convert all of its heat completely in to work. This picture will make you understand Kelvin Planck’s statement very easily. This figure shows that the engine is continuously taking heat from the heat source and converting this heat into equal amount of work. This phenomenon is possible according to 1st law of thermodynamics as energy is conserved. But it does not obey the Kelvin-plank statement of second law.   Thus, Kelvin Planck’s statement simply wants to say that – “ A heat engine must exchange the heat with at least two thermal reservoirs, one at higher temperature and other at lower temperature, then only the engine will operate ”.  This type of heat engine (as shown in above figure) is possible according to the st...

Since, we know that thermodynamics is concerned with the conversion of heat into work and work into heat. That's why we need a machine that converts heat into work. That is a HEAT ENGINE . Engine is the heart of any vehicle.    ......." A heat engine is a machine that operates between two reservoirs in which one acts as a heat source while the other acts as a heat sink. Its function is to convert heat into work by absorbing heat from the heat source and transfer the remainder to the heat sink after producing work from heat "......... Another thing to remember is that heat cannot be completely converted into work. Every single thermodynamic system exists in a particular state. When a system passes through a series of different states and finally returns to its initial state, a thermodynamic cycle is said to have occurred. In the process of going through this cycle, the system can do work on its surroundings, for example by moving a piston, thereby acting as a heat engine. ...

Since, we know that thermodynamics is concerned with the conversion of heat into work and work into heat. That's why we need a machine that converts heat into work and work into heat. " A heat engine is a machine that converts heat into work whereas a heat pump or refrigerator is a machine that converts work into heat ".  Here, we use both the laws of thermodynamics (1st law and 2nd law) to understand the working operation of a Heat-Pump/Refrigerator. The first law of thermodynamics tells us about the conservation of energy while the second law of thermodynamics tells us about the direction of energy transfer.  What Is Heat Pump ??? In a heat engine, we saw that heat transfer takes place from a higher temperature body to a lower temperature body and the device or machine produces some useful work. And that’s obviously right.   But what if we want to transfer the heat in the reverse direction ,i.e, from lower temperature body to higher temperature body??? Heat transfer nev...

Entropy is an intrinsic property of a substance and is not affected by the external position of a system or its motion relative to other systems. It is a measure of the randomness of the system. Thus, the higher the randomness of the system, the higher the entropy of the system and the lower the randomness of the system, the lower the entropy of that system. Entropy   " Entropy is defined as a measure of the system's thermal energy that is incapable of doing work ". It is a state function.  For Example Heat is a form of energy that is incapable of doing work. Therefore, the more heat added to the system (or tranfer from the system), the higher (or the lower) will be its entropy.  The formula for change in entropy is given by the equation;                      ➩ ∆S = ∆Q/T For a reversible process, the change in entropy is given as; The Total Change In Entropy Entropy change is zero at equilibrium condition or whenev...