Thermodynamics
Thermodynamics
- Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy and matter.
Laws of Thermodynamics
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The 0th law of thermodynamics states that if two separate systems are in thermal equilibrium with a third system, they are in thermal equilibrium with each other. This forms the basis of temperature measurement.
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The first law of thermodynamics, also known as Law of Energy Conservation, states that energy cannot be created or destroyed in an isolated system.
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The second law of thermodynamics claims that the entropy of an isolated system always increases. This law shows the asymmetry between forward and backward time directions.
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The third law of thermodynamics states that the entropy of a perfect crystal at absolute zero is exactly equal to zero.
Heat and Work
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Heat is the transfer of energy due to a temperature difference. It is denoted by ‘Q’.
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Work is the transfer of energy by any process other than heat. It can be calculated using the formula W = Fd, where F is force and d is distance moved in direction of force.
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Both heat and work are ways in which a system can transfer energy.
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The total energy of a system is conserved. If the system does work on its surroundings or gives off heat, its internal energy will decrease.
Entropy
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Entropy (S) is a measure of the randomness or disorder of a system. It increases as a system’s temperature increases.
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Entropy is also a state function, meaning its value depends only on the state of the system and not on how that state was achieved.
Heat Engines
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A heat engine is a device that converts heat to work. It operates between two heat reservoirs. Heat is absorbed from the high temperature source, and part of this energy is converted into work- the rest is rejected to the low temperature sink.
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The efficiency of a heat engine is defined as the useful work done compared with the heat input. It is given by efficiency = (Work output / Heat input) x 100%.
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The Second Law of Thermodynamics imposes a limit on the maximum possible efficiency of a heat engine.
Carnot Cycle
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The Carnot Cycle is the ideal operating cycle for a heat engine and it consists of two isothermal processes and two adiabatic processes.
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The engine with the Carnot cycle has the highest efficiency of any heat engine operating between two given temperatures.
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This cycle helps understand the maximum possible efficiency a heat engine can achieve.