Electrostatic/electrical units

EMU, the electromagnetic system of electrical units based on dynamics. ESU, the electrostatic system of electrical units based on static data. 

This chapter is the only place in this volume that we encounter electrical units. Certain equations in electrostatics differ by the factor 47t, depending on whether they are written for SI or cgs units. To help clarify this situation, the chapter contains an appendix on electrical units which may be helpful, particularly when references based on other units are consulted. 

ESU, the electrostatic system of electrical units based on static data. 

Electrical Units. They may be subdivided into EMU (emu)-electromagnetic and ESU (esu electrostatic units. EMU ate based on the strength of magnetic poles (m and m ) ... 

Electrostatic Units (ESU or esu). See under Electrical Units and also under Electrostatic Law of Coulomb... 

Voltages given in this section are electrostatic unless otherwise specified. A discussion of electrical units will be found later in this chapter. 

Electric displacement D Electrostatic cgs unit Electromagnetic cgs unit... 

The cgs electrical units are such that when charge is given in electrostatic units and field strength is in statvolts per centimeter, the resulting force is in dynes. The direction of the force is the same as the field except that negatively charged particles will be attracted toward the positive end of the field, and vice versa. 

Electrical unit Absolute unit Electrostatic unit... 

SOLUTION. The main points of interest are the mixed electrical and mechanical units. Following the customary practice in the field. (2.38) and (2.42) are based on electrostatic (esu) units. Thus when E is expressed in statvolts/cm and the mechanical parameters are expressed in cgs units, the charge e is in statcoulombs. Moreover,... 

The electrical units require some special discussion. The force of attraction or repulsion between charged bodies was first used by the French engineer Charles Coulomb 1736-1806 as the basis for the definition of the unit of charge. He defined the electrostatic unit (esu) of charge as... 

Here, F, R, and T denote the Faraday constant, the molar gas constant, and the absolute temperature, respectively. The parameter is the static permittivity of the liquid, the bulk concentration of the ionic species i, and Zt its valency. Note that SniSo is replaced by s An when an unrationalised notation of electric quantities, e.g., in electrostatic CGS units, is employed (cf. Hunter 1988, pp. 357). 

The electrostatic potential within a phase, that is, l/e times the electrical work of bringing unit charge from vacuum at infinity into the phase, is called the Galvani, or inner, potential Similarly, the electrostatic potential difference... 

The carbon black (soot) produced in the partial combustion and electrical discharge processes is of rather small particle si2e and contains substantial amounts of higher (mostly aromatic) hydrocarbons which may render it hydrophobic, sticky, and difficult to remove by filtration. Electrostatic units, combined with water scmbbers, moving coke beds, and bag filters, are used for the removal of soot. The recovery is illustrated by the BASF separation and purification system (23). The bulk of the carbon in the reactor effluent is removed by a water scmbber (quencher). Residual carbon clean-up is by electrostatic filtering in the case of methane feedstock, and by coke particles if the feed is naphtha. Carbon in the quench water is concentrated by flotation, then burned. 

The potassium combines with the sulfur to form potassium sulfate, which condenses as a soHd primarily in the electrostatic precipitator (ESP) or baghouse. The recovered potassium sulfate is then deUvered to a seed regeneration unit where the ash and sulfur are removed, and the potassium, in a sulfur-free form such as formate or carbonate, is recycled to the MHD combustor. It is necessary also to remove anions such as Cf and E which reduce the electrical conductivity of the generator gas flow. These are present in the coal ash in very small and therefore relatively harmless concentrations. As the seed is recycled, however, the concentrations, particularly of CF, tend to build up and to become a serious contaminant unless removed. 

Molecules do not consist of rigid arrays of point charges, and on application of an external electrostatic field the electrons and protons will rearrange themselves until the interaction energy is a minimum. In classical electrostatics, where we deal with macroscopic samples, the phenomenon is referred to as the induced polarization. I dealt with this in Chapter 15, when we discussed the Onsager model of solvation. The nuclei and the electrons will tend to move in opposite directions when a field is applied, and so the electric dipole moment will change. Again, in classical electrostatics we study the induced dipole moment per unit volume. 

The symbols 5+ and 5- indicate polarity of the two ends or poles of the electrically neutral molecule. Such a polar molecule constitutes a permanent dipole, i.e., two equal and opposite charges (e) separated by a distance (d) in space. A quantitative measure of the polarity of a molecule is the dipole moment (p in Debye units), which is defined as the product of the charge (e in electrostatic units) and the distance (d in cm). 

The authors provide selection criteria, by which the suitability of a process for a distributed production can be assessed [139]. These are explicitly given for the categories of feedstock, processes, customer products, and waste products. This is completed by a list of suitable device types for distributed production such as plate heat exchangers, pressure and temperature swing units, electrostatic dispersers, and membrane units. The various operations often rely on the use of electricity and therefore are said to be particularly suited for operation at the mini scale. 

Conductivity is a very important parameter for any conductor. It is intimately related to other physical properties of the conductor, such as thermal conductivity (in the case of metals) and viscosity (in the case of liquid solutions). The strength of the electric current I in conductors is measured in amperes, and depends on the conductor, on the electrostatic field strengtfi E in tfie conductor, and on the conductor s cross section S perpendicular to the direction of current flow. As a convenient parameter that is independent of conductor dimensions, the current density is used, which is the fraction of current associated with the unit area of the conductor s cross section i = I/S (units A/cnF). 

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