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Thermodynamics

Thermogram Thermogram The colors in the thermogram (above images) indicate where the heat is being released, red and orange indicate warm spots; blue and purple indicate the cooler regions. The science of heat and energy is what exactly is the heart of this topic. Lets step in to discover more.

Learning objectives

After completing the topic, the student will be able to:

  • Observe and explore how steam engine works, based on the laws of thermodynamics.
  • Investigate how internal energy helps in understanding first law of thermodynamics.
  • Explore and investigate different types of thermal process and analyze the work done in each of the process to relate to the daily life applications.
  • Explore and investigate how air conditioners work using the second law of thermodynamics.
  • Understand the concept of entropy, and its importance in exploring the second law of thermodynamics.
  • Probe how thermal equilibrium helps in understanding zeroth law of thermodynamics.
  • Understand and explore superconductivity using third law of thermodynamics and its importance to the real world.
Steam engine Laws of thermodynamics The steam train pulling a load above is an excellent example of how the concept of thermodynamics function in regard to work. The scientific field of thermodynamics examines 'heat power' in regards to an ability to do work and the conversion of heat to other forms of energy. The laws and mathematical formulas of thermodynamics are as fundamental and absolute as science is able to produce. All things in the observable universe follow these laws including the weather on earth driven by the heat of the sun, plants producing food using solar energy, and biological functions in the cells of the body which use heat stored in molecules.
Thermodynamics

In the 17th century, it was accidentally discovered that heat could perform work. It was a surprise because until that time heat was only used to cook food, to melt and forge metals. Its a common experience to most of us to observe that a lid placed on container of boiling water is lifted up and even some times thrown off due to the steam. This is because, when water is converted into water vapor, it expands and occupies a greater volume.

This observation that steam could be used to push something, that is steam can do work, led to design of machine which converts energy stored in steam into mechanical work. Such a device is called an engine.

The study of heat and its transformation to mechanical energy is called Thermodynamics (in Greek meaning "movement of heat"). We have discussed earlier that work is done when energy is transferred from one object to another by mechanical means. In the same way heat is transferred from objects at higher temperature to those at lower temperatures. Thus, 'heat' is much like 'work'. Thermodynamics largely studies how heat can be used efficiently for moving bodies and doing work.

Thermodynamics employs only macroscopic notions – such as mechanical work, pressure and temperature – and their roles in energy transformations. Thermodynamics is a powerful theoretical science that bypasses the molecular details of the system altogether. Its foundation is the conservation of energy and the fact that heat flows spontaneously from hot to cold and not the other way round. It provides the basic theory of heat engines – from steam turbines to fusion reactors and the basic theory of refrigerators and heat pumps.

Thermodynamic System Open, closed and isolated systems Hot coffee in a beaker is an example of open system. Stoppered glass flask of hot coffee is an example of closed system. Vacuum flask of hot coffee is an example of an isolated system.
Basic terms

System: By thermodynamic system we mean some specified amount of matter treated as separate from the rest of the universe for the purpose of describing its behaviour. It is important to identify the system precisely. For example, a certain amount of a gas enclosed in a cylinder fitted with a piston is a common example of a thermodynamic system. Ordinarily, the gas constitutes the system; the walls of the container, the piston etc., are not included in the system. But, in some situations, one may find it convenient to include the walls also in the system.

Surroundings or environment: Anything outside the system, which exchanges energy with the system and thus affects the behavior of the system is called the surroundings or environment of the system. Thus, for the system consisting of only the gas in a container, the container and the piston form the surroundings. Everything else, which does not interact with the system, is usually referred to as 'the rest of the universe'.

Universe: The system and its surroundings together is called the universe.

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