# Applications of second law of thermodynamics

### APPLICATIONS OF SECOND LAW OF THERMODYNAMICS

Abstract: Second law says that entropy for eternity increases & holds the supreme position among the laws of Nature. It is the basis of construction of many machines such as refrigerators, heat pump etc

### Introduction

The second law of thermodynamics is also identified as the entropy law. It was formulated in the middle of the last century by Clausius & Thomson .This idea was conceived from Carnot's earlier study like the fall or flow of a stream that turns a mill wheel & the "fall" or flow of heat from higher to lower temperatures that motivates a steam engine. It states that "Every process in this universe toward the direction of increase of entropy"

Entropy refers to the level of disarray of a system. The higher the uncertainty of a system, the higher is its entropy. The more ordered a system, the inferior its entropy. A "system" is the division of the world we are concerned in. Its size can vary from a single molecule or as big as the complete cosmos.

Knowledge of this law can be applied to situations such as black hole thermodynamics, working of refrigerators, Heat Pumps, predict the direction of a reaction etc.

The adjacent image indicated pictorially what do we mean by entropy and we can think of these balls homologous to air molecules or kind of energy distribution here like as soon as the partition between the balls was removed the balls arranged themselves randomly so that they are far away from each other (similar ones) similarly when balloon with air is pricked the air moves out of it speedily which means that the air molecules be likely to favour randomness or rise in entropy.

Plenty of examples can be quoted from our experience with the second law of thermodynamics operating. For example; whenever a hot saucepan is positioned in a sink of cold water, the saucepan cools down & temperature of the water rises. Thus the heat energy gets dispersed between the water & the saucepan. In these processes, the entropy of that system increases. The other way, the saucepan to get hotter while the water freezes, never happens because that would necessitate a spontaneous enhancement in union of molecules & energy. Similarly a drop of dye poured in a cup of water will finally result in a consistently coloured solution, even if we never stir the liquid. The dye molecules distribute as evenly as possible throughout the volume of water.

There are two important implications of the second law for studying biochemical reactions:

1. Naturally happening spontaneous processes at all times proceed in the direction of the status that has the least potential energy. An example that can be quoted is water flowing downhill. 2. Naturally occurring chemical reactions tend to increase the disorder in the universe. The first law of thermodynamics states that energy cannot be vanished, but it can certainly change form. Whenever a reaction is finished some of the energy is lost, this energy is constructive for doing more work. But some part of energy is at all times certainly wasted in the form of heat. An example is the translation of the energy in gasoline to power in an automobile. Only about 20% of the energy results in activity of the automobile & the rest of the energy is lost as heat.

### Applications of Second Law

1. Heat Engines: In the case of Heat Engines Second Law of Thermodynamics states that it is impossible to remove a quantity of heat, say QH, from a hot pool & make use of it all to do work, say W. Some quantity of heat, say QC, must be bushed to a cold reservoir. This is also called the Kelvin-Planck statement of the second law of thermodynamics.

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