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]]>Heat is a type of energy that is transferred from one body to another due to difference in temperature. Heat always flows from a hotter object to a colder object until they reach a state of thermal equilibrium. The measure of the average heat in a substance is called temperature.
Thermodynamics is a branch of physics that studies about heat and the effects of changes in temperature, pressure, and volume on physical systems at the macroscopic scale.
“French mechanical engineer and physicist Nicolas Leonard Sadi Carnot is known as the the father of thermodynamics.” For publishing Reflections on the Motive Power of Fire in 1824.
Aristotle (ancient Greek philosopher) believed that a vacuum, or a space without matter was is impossible because “nature abhors a vacuum”. Aristotle believed that empty space could not exist, because nature continually fills any empty space with denser surrounding material, preventing a true void. According to Aristotle, a vacuum was an illogical concept, that would allow for impossible motion.
Otto von Guericke’s ( German scientist, inventor, and politician) invention (the world’s first vacuum pump in 1650) and his famous Magdeburg Hemisphere experiment proved Aristotle’s theory wrong.
Robert Boyle and his colleague Robert Hooke used this vacuum pump, based on Otto von Guericke’s design, for experiments. This led to the development of a law known as Boyle’s Law. Which states that the pressure of a fixed amount of gas is inversely proportional to its volume at constant temperature.
In 1698 Thomas Savery invented the first commercially used steam-powered device, a steam pump known as the Miner’s Friend. His invention was a water pump that would draw water up by creating a vacuum using condensed steam and then push the water out using the pressure of the steam.
Then later inventors such as Thomas Newcomen and James Watt used Savory’s work to develop more efficient and powerful steam engines.
Limitations of Savery’s engine: Savery’s engine was dangerous. It was not very safe because of the risk of boiler bursting from the high steam pressure, and its pumping height was also limited. In addition, it was inefficient.
Thomas Savory’s design was to create a vacuum by using steam to pump water. On the other hand, another inventor, Thomas Newcomen, improved the efficiency by adding a piston to separate the steam from the water in 1712. This improvement made it safer than Savory’s design.
Thomas Newcomen’s atmospheric engine became the first widely successful steam engine. It was widely used for mine drainage and set the stage for later innovations.
Limitation of Thomas Newcomen’s engine: Newcomen’s engine was safer and more efficient, but was still inefficient. Newcomen’s engine were inefficient due to the repeated heating and cooling of the cylinders, wasting a lot of energy
Since, Newcomen’s engine were inefficient James Watt realised that the cylinder could stay hot if the steam was condensed in a separate chamber, away from the main cylinder. James Watt realized that if the steam was condensed in a separate chamber away from the main cylinder, the cylinder could stay hot.
This idea was influenced by Black’s work on latent heat. It was the first major improvement to the steam engine. It made the engines much more efficient, saving three-fourths of the fuel compared to the Newcomen engines.
“Sadi Carnot’s (father of thermodynamics) 1824 theoretical Carnot engine laid the foundation for modern thermodynamics by introducing the concepts of ideal heat engines, maximum efficiency, and the relationship between heat, work, and temperature..”
Sadi Carnot created the first theoretical framework for a heat engine, establishing the Carnot cycle and the Carnot theorem, which defines the maximum possible efficiency for any heat engine.
He did this by proposing an ideal, reversible engine that operates in a four-step cycle of isothermal and adiabatic expansions and compressions between a hot and cold reservoir, setting a standard of performance that no other engine could surpass.
Before Carnot, there was no way to know the maximum possible efficiency of a heat engine. He provided the scientific basis for this limit, showing that efficiency depends only on the temperatures of the hot and cold reservoirs.
An isolated system cannot exchange energy or mass with its surroundings. This means that neither heat nor work can cross the system’s boundary, and no matter can enter or leave the system. An isolated system in the universe has a definite amount of energy. This energy is called internal energy.
The internal energy is the sum of the kinetic and potential energies. The internal energy of an isolated system is conserved. Because no energy can enter or leave the system.
It consist of a large number of particles(atoms or molecules) and exists in the form of solid, liquid or gas or a combination of two or more states.
Equation of state of the thermodynamic system:
The thermodynamic state of a system is described by four parameters. These parameters are temperature (T), pressure (P), volume (V) and heat content (Q).
the relation between temperature (T), pressure (P), volume (V) and heat content (Q) is called equation of state of the thermodynamic system:
For n moles the equation is-
PV=nRT
P= Pressure, V= Volume, T= Temperature, R= Universal gas constant
When the pressure and volume of a gas change, without any change in its temperature, it is called an isothermal process. It allows the free exchange of heat between the gas and its surroundings. When a gas is compressed in an enclosure, work is done on the gas which generates heat, causing the temperature to rise. The temperature of the gas will remain constant.
Similarly when the pressure on the gas is decreased, it expands, work is done by the gas.Some heat energy is lost and the temperature decreases. Thus, for an isothermal change, there should be a free exchange of heat between the gas and its surroundings.
Hence, the two essential conditions for a perfect isothermal change are:
Examples of Isothermal changes are-
When the pressure and volume of a gas change along with changing temperature it is called an area that a process. When a gas in an enclosure compressed suddenly, heat is produced which if not allowed to escape will increase the temperature of the gas.
Similarly, if the gas is allowed to expand suddenly, heat energy will be spent and the volume of the gas expands. If this heat is not gained from the surroundings, the temperature of the gas would fall. Thus, for an adiabatic process, no change of heat between the gas and the surroundings should take place. Hence, the two essential conditions for a perfect adiabatic change are:
Perfect adiabatic changes are practically impossible. Examples of nearly perfect adiabatic changes are
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