Electromagnetic fields Subject

Metal contained in the channel is subjected to forces that result from the interaction between the electromagnetic field and the electric current in the channel. These inward forces produce a circulation that is generally perpendicular to the length of the channel. It has been found that shaping the channels of a twin coil inductor shown in Figure 10 produces a longitudinal flow within the channel and significantly reduces the temperature difference between the channel and the hearth (12). 

Mass spectrometer (MS) An instrument that identifies substances by causing them to be ionized and subjecting the resulting ions to a strong electromagnetic field. 

The important characteristics of a transducer used in conjunction with an electronic measurement system are accuracy, susceptibility, frequency, impedance and, if appropriate, the method of excitation. The transducer is likely to be the least accurate component in the system, and it should be calibrated (and recalibrated) at frequent intervals. It is likely to be subject to a range of different physical conditions, some of which it is there to detect and others by which it should remain unaffected (for example, a pressure transducer should be unaffected by any changes in temperature which it might be called upon to experience). Some types of transducer are not suitable for use under D.C. conditions and all will have an upper limit of frequency at which accuracy is acceptable. Many types of transducer are also affected by stray electromagnetic fields. 

Suppose now that the system is subjected to an oscillating electromagnetic field with a representative Fourier component of the electric field F0( >] cos cot. The predominant term in the interaction energy V is usually the electric dipole term Ei , e.g. for an electron in an atom... 

The Time Dependent Processes Section uses time-dependent perturbation theory, combined with the classical electric and magnetic fields that arise due to the interaction of photons with the nuclei and electrons of a molecule, to derive expressions for the rates of transitions among atomic or molecular electronic, vibrational, and rotational states induced by photon absorption or emission. Sources of line broadening and time correlation function treatments of absorption lineshapes are briefly introduced. Finally, transitions induced by collisions rather than by electromagnetic fields are briefly treated to provide an introduction to the subject of theoretical chemical dynamics. 

For all of the cases considered earlier, a C(t) function is subjected to Fourier transformation to obtain a spectral lineshape function 1(G)), which then provides the essential ingredient for computing the net rate of photon absorption. In this Fourier transform process, the variable 0) is assumed to be the frequency of the electromagnetic field experienced by the molecules. The above considerations of Doppler shifting then leads one to realize that the correct functional form to use in converting C(t) to 1(G)) is ... 

The phase relations among the scattered wavelets depend on geometrical factors scattering direction, size, and shape. But the amplitude and phase of the induced dipole moment for a given frequency depend on the material of which the particle js composed. Thus, for a full understanding of scattering und absorption by small particles, we need to know how bulk matter responds to oscillatory electromagnetic fields this is the subject of Chapters 9 and 10. 

Our fundamental task is to construct solutions to the Maxwell equations (3.1)—(3.4), both inside and outside the particle, which satisfy (3.7) at the boundary between particle and surrounding medium. If the incident electromagnetic field is arbitrary, subject to the restriction that it can be Fourier analyzed into a superposition of plane monochromatic waves (Section 2.4), the solution to the problem of interaction of such a field with a particle can be obtained in principle by superposing fundamental solutions. That this is possible is a consequence of the linearity of the Maxwell equations and the boundary conditions. That is, if Ea and Efc are solutions to the field equations,... 

Here <( t ) f(t")> is the autocorrelation function of the electromagnetic field. For the case of excitation by a conventional light source, where the amplitudes and the phases of the field are subject to random fluctuations, the field autocorrelation function differs from zero for time intervals shorter than the reciprocal width of the exciting source. In the limit 8v A, that is when the spectral width, 8v, of the source exceeds the inhomogenously broadened line width, the field autocorrelation function can be represented as a delta function... 

Laidlaw was joined by Reginald Paul, his former colleague from the University of Alberta, in 1966. Paul initially worked on the application of field theory to chemical physics. His many papers during the 1970s culminated in the publication of a book on the subject.204 Subsequently, he became interested in studying the interaction of electromagnetic fields with biological cells, and also in theoretical electrochemistry. 

A molecule M plus its bath B in an external field can be described as a total system with a Hamiltonian H = Hm + Hb + H m n I (f) which may depend on time if the total system is subject to an external electromagnetic field, as indicated. Given this, the density operator r(t) for the system satisfies the Liouville-von Neumann (L-vN) equation,... 

If particles are magnetism-sensitive, they are subjected to a magnetic force once they are exposed to an electromagnetic field in a gas-solid flow. The magnetic force, Fm, is given... 

We assume further that this system is subjected to a weak external perturbation. This perturbation may be as weak as one wishes it will be treated semiclassically by a time-dependent hamiltonian (an incident electromagnetic field, for example). 

Nonlinear optical properties arise when materials are subjected to electromagnetic radiation of very high intensity (usually from lasers). Low-intensity electromagnetic fields give a linear response for the induced dipole moment vector in a molecule ... 

Ionic conduction some materials produce electric currents within themselves when subject to electromagnetic fields. When these electric currents flow within the structure of the materials, which in most cases have a relatively high resistivity, the material is heated. 

The rheology of low molecular weight thermotropic compounds has been a subject of considerable theoretical and experimental analysis In general, liquid crystals are easily oriented by surfaces, electromagnetic fields and mechanical stress or shear, and the degree of orientation, in turn, affects their melt viscosity. The rheological behavior of a liquid crystal is known to be greatly dependent on the nature and also on the texture of its mesophase. 

THE ELEMENT OF WORK FOR A SYSTEM SUBJECTED TO ELECTROMAGNETIC FIELDS 29... 

The Element of Work for a System Subjected to Electromagnetic Fields... 

The treatment of thermodynamic characteristics of matter subjected to electromagnetic fields requires considerable care. The next few Sections are devoted to a discussion of this topic for a more complete and systematic exposition the reader is referred to a review article. In this section we deal with several preliminaries that will be generalized later. 

Ionic conduction is the conductive migration of dissolved ions in the applied electromagnetic field. This ion migration is a flow of current that results in PR losses (heat production) due to resistance to ion flow. All ions in a solution contribute to the conduction processes however, the fraction of current carried by any given species is determined by its relative concentration and its inherent mobility in the medium. Therefore, the losses due to ionic migration depend on the size, charge and conductivity of the dissolved ions, and are subject to the effects of ion interaction with the solvent molecules [18]. 

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