Quiz 12: Thermodynamics

Physics & Astronomy

The plot pressure verses volume of a gas at constant temperature is shown in the below figure. The ideal gas equation, the relation among pressure, volume and temperature is, img Here, img is pressure, img is volume, img is number of moles, img is universal gas constant and img is temperature. For a given mass of the gas, the number of moles constant and the value of img is constant for all the gasses. If the temperature of the gas is constant, the volume of the ideal gas is inversely proportional to the pressure on the gas. So, the plot, the pressure verses volume of the gas is a straight line with negative slope. In the above figure, the plot pressure verses volume of the gas is not a straight line, so the above plot pressure verses volume is not for the ideal gas.

The first law of thermodynamics is essentially the principle of conservation of energy, which states that in all transformations, the total heat energy img supplied must be balanced by external work done img plus the increase in internal energy img of the system and expressed as, img Rewrite the equation for work done img . img Substitute img for img , and img for img . img Therefore, the work done by the person in the match is img .

A thermodynamics process is a change in the state of the system. The processes are classified as reversible and irreversible. Reversible process is the process in which the system could be brought back to its initial state along the same path. Every intermediate state along the path in reversible process is under equilibrium state. On a p-V diagram, the state of the system can be represented by coordinates img . Irreversible process can be determined by knowing initial and final states and it is independent of path. Reversible process is given by very intermediate state and it should be in equilibrium which means it is path dependent. Thus, the reversible process is represented on p-V diagram when path is known. Therefore, the correct option is img .