Physics
Interaction Energy
Interaction energy refers to the potential energy associated with the interaction between two or more objects or particles. It arises from fundamental forces such as gravitational, electromagnetic, or nuclear forces. The amount of interaction energy depends on the relative positions and properties of the interacting objects or particles.
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8 Key excerpts on "Interaction Energy"
No longer available |Learn more- (Author)
- 2014(Publication Date)
- White Word Publications(Publisher)
In particle physics, this inequality permits a qualitative understanding of virtual particles which carry momentum, exchange by which and with real particles, is responsible for the creation of all known fundamental forces (more accurately known as fundamental interactions). Virtual photons (which are simply lowest quantum mechanical energy state of photons) are also responsible for electrostatic interaction between electric charges (which results in Coulomb law), for spontaneous radiative decay of exited atomic and nuclear states, for the Casimir force, for van der Waals bond forces and some other observable phenomena. Applications of the concept of energy Energy is subject to a strict global conservation law; that is, whenever one measures (or calculates) the total energy of a system of particles whose interactions do not depend explicitly on time, it is found that the total energy of the system always remains constant. • The total energy of a system can be subdivided and classified in various ways. For example, it is sometimes convenient to distinguish potential energy (which is a function of coordinates only) from kinetic energy (which is a function of coordinate time derivatives only). It may also be convenient to distinguish gravitational energy, electric energy, thermal energy, and other forms. These classifications overlap; for instance, thermal energy usually consists partly of kinetic and partly of potential energy. • The transfer of energy can take various forms; familiar examples include work, heat flow, and advection, as discussed below. ________________________ WORLD TECHNOLOGIES ________________________ • The word energy is also used outside of physics in many ways, which can lead to ambiguity and inconsistency. The vernacular terminology is not consistent with technical terminology.
eBook - ePub- E. Atlee Jackson(Author)
- 2012(Publication Date)
- Dover Publications(Publisher)
Some of these limitations due to quantum-mechanical effects will be taken up in Section 5. Before considering the interaction between particles, we should first define the kinetic and potential energy of a collection of noninteracting particles (they do not exist, of course, but it is often useful to consider such a model). If a system contains N particles, the total kinetic energy is defined simply as the sum of the individual kinetic energies of the particles: (16) where m i, v i) is the mass and velocity of particle i. Moreover, if these particles are in an external (conservative) force field, such as an electric field or gravity, then the total potential energy due to these forces is again the sum of their individual potential energies: (17) Note that, just as E kin depends on the value of each velocity v i, φ ext depends on the position of each particle r i. Now we turn to the question of the interactions between particles and between molecules. Just as we can describe conservative external forces in terms of a potential energy Φ (r i), we can frequently represent the intermolecular forces by a potential energy Φ(r ij). In this case r ij = r i − r j = [(x i − x j) 2 + (y i − y i) 2 + (z i − z i) 2 ] 1/2 is the distance between the molecules, and the force on particle i (due to particle j) is given by If the potential depends only on the magnitude of the separation between the molecules, then (18) and the force is along their connecting line, as illustrated in Figure 4. Note that F i = − F j, so the forces are equal but in opposite directions. Figure 4. Intermolecular forces The intermolecular forces can be conveniently divided into repulsive forces and attractive forces. These repulsive forces may originate in electrical forces, nuclear forces, or certain quantum-mechanical effects. For example, when two neutral atoms come very close together, the electrons around each atom begin to overlap
eBook - PDF- Ruth W. Chabay, Bruce A. Sherwood(Authors)
- 2015(Publication Date)
- Wiley(Publisher)
But the surroundings did no work! The change in kinetic energy of the system is not equal to the work done by the surroundings. Before deciding that the Energy Principle has been violated, we should consider the possibility that we have overlooked a kind of energy that is present in systems containing more than one interacting object. In fact, this is the case. Earth Ball System F net = 0 W = 0 Figure 6.23 As the ball falls no work is done on the system of (Ball + Earth) because there are no significant interactions with the surroundings. Potential Energy Belongs to Pairs of Interacting Objects In any system containing two or more interacting particles, such as compressed or stretched springs, galaxies of stars interacting gravitationally, or atoms in which the protons and electrons interact electrically, there is energy associated with the interactions between pairs of particles inside the system. This Interaction Energy is not the same as the rest energies or kinetic energies of the individual particles. We call this pairwise Interaction Energy “potential energy.” Traditionally potential energy is represented by the symbol U. Since the system of (Ball + Earth) contains two interacting objects, its energy is really this: E sys = (m ball c 2 + K ball ) + (m Earth c 2 + K Earth ) + U ball-Earth A change in potential energy is associated with a change in the separation of interacting objects. We can think of separation changes as change in the shape of the multiparticle system, such as the ball and Earth moving closer together, a spring stretching or compressing, or an electron moving away from a proton. In the case above, as the ball and the Earth get closer together, the kinetic energy of the system increases, but we will see that the potential energy (Interaction Energy) decreases.
eBook - PDF- Yuri A Berezhnoy(Author)
- 2005(Publication Date)
- WSPC(Publisher)
Chapter 2 Fundamental Interactions 2.1 Gravitational Interaction Physics is concerned with matter: its structure and motion. The motion of matter is due to certain forces acting between bodies. The motion of galaxies and stars, of planets and comets, of electrons in TV sets and atoms, of nucleons and quarks in atomic nuclei, radioactive decays of atomic nuclei and elementary particles as well as all various processes in the Universe are caused by interactions between different physical objects. So it is not surprising that some of the most important questions in physics pertain to the study of these interactions. Over two millennia ago, the Greek philosopher Aristotle theorized that all substance in the Universe consisted of four elements — earth, air, fire, and water — and that these were subject to the action of two forces. The first was the force of gravity, which attracted earth and water downwards. The second was a force of lightness, which served to attract fire and air upwards. Thus, Aristotle divided all of Nature into substances and forces. This approach has persisted in physics until the present day. Now, there are four known types of interactions: gravitational, electromagnetic, and the strong and weak nuclear forces. Let us consider each in turn. The gravitational interaction, by intensity, is the weakest of all the in-teractions known to us. The gravitational forces have a universal character. This means that all matter is subject to them; this is what the law of univer-sal gravitation states. The range of gravitational forces is infinite. Gravita-tional forces are attractive. Gravitational interaction is mainly manifested between macroscopic bodies; it determines the motions of various cosmic objects: galaxies, stars, planets, etc. In the world of elementary particles, gravitational interaction is not directly apparent because of the very small 41 42 The Quantum World of Nuclear Physics masses of the particles.
eBook - ePubEnergy Storage
A New Approach
- Ralph Zito, Haleh Ardebili(Authors)
- 2019(Publication Date)
- Wiley-Scrivener(Publisher)
The history of the development of physical concepts is not the prime concern here, but some knowledge of their evolution does serve to bring more closely to our attention and scrutiny a better appreciation of terms that we employ daily. Sometimes it is necessary to begin understanding or developing a body of knowledge in order to make certain basic assumptions on an entirely intuitive basis. As scientifically unsatisfying as that may be, it is unavoidable at times. One could draw a weak comparison to plane geometry (Euclid) with regard to its various axioms and the declaration that parallel lines never meet. Even the concept of straight lines is rather intuitive in nature.Perhaps the best definition is that a force is required to change the motion of a body. Many problems arise in finding acceptable definitions for the basic parameters of physical science, namely, the abstract concepts of mass, time, force, and energy. However, we must learn to be satisfied with definitions that leave something to be desired in order to move on toward generating a working body of mechanics that enables us to design and build practical devices that serve our purposes.An interesting definition of energy comes from the Grolier Encyclopedia, which states:Energy can be measured in terms of mechanical work, but because not all forms of energy can be converted into useful work, it is more precise to say that the energy of a system changes by an amount equal to the net work done on the system … In classical physics, energy, like work, is considered a scalar quantity; the units of energy are the same as those of work. These units may be ergs, joules, watt-hours, foot-pounds, or foot-poundals, depending on the system of units being used. In modern science, energy and the three components of linear momentum are thought of as different aspects of a single four-dimensional vector quantity, much as time is considered to be one aspect of the four-dimensional space-time continuum … Energy exists in many different forms. The form that bodies in motion possess is called kinetic energy. Energy may be stored in the form of potential energy, as it is in a compressed spring. Chemical systems possess internal energy, which can be converted by various devices into useful work; for example, a fuel such as gasoline can be burned in an engine to propel a vehicle. Heat energy may be absorbed or released when the internal energy of a system changes while work is done on or by the system. (1993)
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Learning Press(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter- 2 Binding Energy and Kinetic Energy Binding energy Binding energy is the mechanical energy required to disassemble a whole into separate parts. A bound system typically has a lower potential energy than its constituent parts; this is what keeps the system together- often this means that energy is released upon the creation of a bound state. The usual convention is that this corresponds to a positive binding energy. ________________________ WORLD TECHNOLOGIES ________________________ In general, binding energy represents the mechanical work which must be done against the forces which hold an object together, disassembling the object into component parts separated by sufficient distance that further separation requires negligible additional work. At the atomic level the atomic binding energy of the atom derives from electromagnetic interaction and is the energy required to disassemble an atom into free electrons and a nucleus. Electron binding energy is a measure of the energy required to free electrons from their atomic orbits. This is more commonly known as ionisation energy. At the nuclear level, binding energy is also equivalent to the energy liberated when a nucleus is created from other nucleons or nuclei. This nuclear binding energy (binding energy of nucleons into a nuclide) is derived from the strong nuclear force and is the energy required to disassemble a nucleus into the same number of free unbound neutrons and protons it is composed of, so that the nucleons are far/distant enough from each other so that the strong nuclear force can no longer cause the particles to interact. In astrophysics, gravitational binding energy of a celestial body is the energy required to expand the material to infinity.
- Keith Stowe(Author)
- 2007(Publication Date)
- Cambridge University Press(Publisher)
Conduction involves collisions between particles. Radiation involves the emission of electromagnetic waves by accelerating charges and the absorption of this energy by charged particles that these waves encounter. Convection involves energy transfer of particles as they enter or leave a system. Work is achieved by the action of a force over a distance. Many different kinds of force may act on a system, but the work done has the same general form --the product of an external force and the change in the conjugate internal coordinate. It is customary to use p d V as the prototype for mechanical interactions. Q represents heat added to the system, and W represents work done by the system. Therefore (equation 5.2) E = Q − W (thermal and mechanical interactions). Interactions between systems 83 C Particle transfer --the diffusive interaction C.1 The chemical potential We now examine the diffusive interaction. When particles enter a system they may carry energy in different ways, two of which we have already encountered: heat transfer and work. Any energy transfer that is not due to either of these mecha-nisms is described by the “chemical potential” µ as follows. When N particles enter a system, the energy delivered via this third mechanism is given by E = µ N (diffusive interaction only; no work or heat transfer). (5.4) To understand this term, we first review the two types of energy transfer that are excluded. As you well know, work is the product of force times distance. Perhaps, though, you have not yet encountered a formal definition of heat. Two important aspects of heat that will be introduced and quantified in future chapters are the following. (1) A heat input increases the number of states accessible to a system. 3 (You might think of this as allowing the particles more ways to wiggle and jiggle.) (2) As we will learn in subsection 9B.1 (equation 9.6), there are three different ways in which heat ( Q ) may enter or leave a system.
eBook - PDFThermodynamics and Statistical Mechanics
An Integrated Approach
- M. Scott Shell(Author)
- 2015(Publication Date)
- Cambridge University Press(Publisher)
This division itself is an approximation, since the Schrödinger equation makes no such distinction. It is, however, a convenient way to think about contributions to interaction energies. A schematic representation of the different contributions is given in Fig. 3.2. The bonded interactions typically describe the change in potential energies due to the following effects. Bond stretching. A common functionality is u ¼ a(d d 0 ) 2 , where d is the length of the bond and a and d 0 are constants. Bond-angle bending. Deviations from a preferred hybridization geometry (e.g., sp 3 ) should incur energetic penalties. A common form is u ¼ b(θ θ 0 ) 2 , where θ is the bond angle formed by three atoms and b and θ 0 are constants. Bond torsions. These interactions occur among four atoms and account for the energies of rotations along a central bond. A common approximation is a cosine expan- sion, u ¼ X n c n cos ðωÞ n , where ω is the torsional angle, n is a summation index, and c n are summation coefficients. On the other hand, the nonbonded interactions apply to atoms that are not connected by bonds, either within the same molecule or in two different molecules. The most frequent kinds of nonbonded energies are the following. Electrostatics. In the classical approximation atoms can have charges, which may be formal (integer) charges due to ionized groups or partial (fractional) ones due to polarization among atoms with different electronegativities. Atoms with charges interact through Coulomb’s law, u ¼ q i q j /(4πϵ 0 r ij ) for atoms i and j separated by distance r ij . This interaction is pairwise between atoms. Van der Waals attractions. Correlations between the instantaneous electron densities surrounding two atoms gives rise to an attractive energy. This is a general attractive 27 3.2 The classical picture
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