UY1: Adiabatic Process

In an adiabatic process, there is no heat exchange between the system and its surroundings (Q = 0). For such a process, the first law gives ΔE = W. This means that the internal energy increases if work is done on the system, and this usually leads to a temperature rise. If work is done by the system, the internal …

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UY1: Isothermal Process

In an isothermal process, the temperature of the system is unchanged. (ΔT = 0). For this process, the first law gives ΔE = 0, thus Q = -W. This means that the net heat input into the system equals to the net work output by the system. From the ideal gas equation, P1V1 = P2V2 = nRT (isotherm). Isothermal work done …

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UY1: Concept of heat engines and heat pumps

A heat engine is a device that converts heat into mechanical energy. Conceptualising the heat engine: The heat engine must carry a working substance (usually a gas) through a cyclic process in which the system passes through a series of states. During the cycle:  the working substance absorbs heat (Qh) from a hot reservoir converts part of that heat into …

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UY1: More about internal energy

The internal energy of a system of a system is the microscopic energy associated with the particles in the system. This includes the translational, rotational, vibrational energy of these particles, the inter-particle potential energy, as well as the energy of their electrons and their nuclei. – It does not include the macroscopic kinetic energy associated with the translation or rotation …

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UY1: Cyclic processes

Although both heat and work involved in the transformation of a system from one state to another is path-dependent, the quantity “Q + W” is experimentally found to be path-independent. In other words, Q + W depends only on the initial and final states of the system! For a cyclic process (i.e., a process that starts and returns to the …

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UY1: Reversible & Irreversible Thermodynamic Processes

Reversible Thermodynamic Processes A reversible transformation is an idealised transformation in which the system is in (very nearly) thermodynamic equilibrium throughout the transformation. – Therefore the system has well-defined values for all its state variables throughout the transformation. – The transformation can be plotted and thus followed on a diagram of state variables. – The system can return to its …

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