Lecture

Energy Conservation: The First Law of Thermodynamics

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Description

This lecture discusses the first law of thermodynamics, focusing on energy conservation. The instructor begins by reviewing the fundamental laws of physics, emphasizing mass conservation and Newton's second law before introducing the Reynolds transport theorem for energy conservation. The lecture defines total specific energy and its components: internal energy, kinetic energy, and potential energy. The instructor explains how energy changes within a system, detailing the contributions of heat transfer and work done on the system. The first law of thermodynamics is presented as a Lagrangian law for fluid systems, highlighting the rate of change of total energy. The discussion includes the concept of mechanical power, differentiating between shaft power and power due to normal stresses. The lecture concludes by relating the energy equation to the Bernoulli equation, illustrating how energy conservation principles apply to fluid dynamics and emphasizing the importance of understanding losses due to viscosity. The instructor encourages students to practice applying these concepts in exercises.

Official source

Ontological neighbourhood

Physics

Mechanics: Fluid mechanics, Classical mechanics

Thermodynamics: Statistical mechanics

Related concepts (32)

Fluid dynamics

In physics, physical chemistry and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids—liquids and gases. It has several subdisciplines, including aerodynamics (the study of air and other gases in motion) and hydrodynamics (the study of liquids in motion). Fluid dynamics has a wide range of applications, including calculating forces and moments on aircraft, determining the mass flow rate of petroleum through pipelines, predicting weather patterns, understanding nebulae in interstellar space and modelling fission weapon detonation.

First law of thermodynamics

The first law of thermodynamics is a formulation of the law of conservation of energy, adapted for thermodynamic processes. A simple formulation is: "The total energy in a system remains constant, although it may be converted from one form to another." Another common phrasing is that "energy can neither be created nor destroyed". While there are many subtleties and implications that may be more precisely captured in more complex formulations, this is the essential principle of the First Law.

Internal energy

The internal energy of a thermodynamic system is the energy contained within it, measured as the quantity of energy necessary to bring the system from its standard internal state to its present internal state of interest, accounting for the gains and losses of energy due to changes in its internal state, including such quantities as magnetization. It excludes the kinetic energy of motion of the system as a whole and the potential energy of position of the system as a whole, with respect to its surroundings and external force fields.

Conservation of mass

In physics and chemistry, the law of conservation of mass or principle of mass conservation states that for any system closed to all transfers of matter and energy, the mass of the system must remain constant over time, as the system's mass cannot change, so the quantity can neither be added nor be removed. Therefore, the quantity of mass is conserved over time. The law implies that mass can neither be created nor destroyed, although it may be rearranged in space, or the entities associated with it may be changed in form.

Thermodynamics

Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed by the four laws of thermodynamics which convey a quantitative description using measurable macroscopic physical quantities, but may be explained in terms of microscopic constituents by statistical mechanics.

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