Electric fields, alignment

Only at extremely high electric fields are the water molecules fiilly aligned at the electrode surface. For electric fields of the size normally encountered, a distribution of dipole directions is found, whose half-widtli is strongly dependent on whether specific adsorption of ions takes place. In tlie absence of such adsorption the distribution fiinction steadily narrows, but in the presence of adsorption the distribution may show little change from that found at the PZC an example is shown in figure A2.4.10 [30]. 

Let us consider the electric field due to a dipole /x aligned along the z axis. The magnitude of the electric field at a point P due to the dipole (see Figure 4.27) is ... 

The direction of the alignment of magnetic moments within a magnetic domain is related to the axes of the crystal lattice by crystalline electric fields and spin-orbit interaction of transition-metal t5 -ions (24). The dependency is given by the magnetocrystalline anisotropy energy expression for a cubic lattice (33) ... 

When the electric field is not aligned with the magnetic field, the conductivity is not independent of the magnetic field. Eor example, if the total electric field E is perpendicular to the magnetic field, in thejy-direction, then E" = E and E = E = 0. Then equations 39 become... 

Liquid crystal displays depend upon the reorientation of the director , the defining alignment vector of a population of liquid crystalline molecules, by a localised applied electric field between two glass plates, which changes the way in which incident light is reflected directional rubbing of the glass surface imparts a... 

Fig. 13. Electric-field dependence of the emission current obtained for a carefully aligned MWCNT film [38], Inset Fowler-Nordheim plot, where y is the field-enhancement factor.

Note that majority electrons that are accelerated by the electric field in one of the cobalt layers contribute to the current, not only in that layer (I = J) but in other layers as well, including the copper layers and the cobalt layers on the other side of the copper. On the other hand, minority electrons that are accelerated by a field in one of the cobalt layers contribute very little to the conductivity in the copper or in the cobalt on the other side of the copper. For anti-parallel alignment of the moments, electrons that are accelerated by the field in one cobalt layer contribute to the current in that layer and in the cobalt, but not in the other cobalt layer. The difference in the lolal current due to both channels between parallel and anti-parallel alignment is almost entirely non-local. It comes from those electrons that are accelerated by the applied electric field in one cobalt layer and propagate across the copper to the other cobalt layer where they contribute to the current. It is clear from Figures 1-4 that this process occurs primarily for majority electrons and for the case of parallel alignment. 

Orientation of polar molecules in an electric field. With the field off. polar molecules are randomly orientad. With the field on, polar molecules such as HF align their positive and negative ends toward the negative and positive poles of tire field, respectively. Nonpolar molecules such as H2 do not line up. 

The electric field of plane-polarized light oscillates in a single plane. It can be prepared hy passing ordinary, unpolarized light through a polarizer, which consists of a material that allows the light to pass only if the electric field is aligned in a certain direction. 

Optical and electro-optical behavior of side-chain liquid crystalline polymers are described 350-351>. The effect of flexible siloxane spacers on the phase properties and electric field effects were determined. Rheological properties of siloxane containing liquid crystalline side-chain polymers were studied as a function of shear rate and temperature 352). The effect of cooling rate on the alignment of a siloxane based side-chain liquid crystalline copolymer was investigated 353). It was shown that the dielectric relaxation behavior of the polymers varied in a systematic manner with the rate at which the material was cooled from its isotropic phase. 

The response of liquid crystal molecular orientation to an electric field is another major characteristic utilised for many years in industrial applications [44] and more recently in studies of electrically-induced phase transitions [45]. The ability of the director to align along an external field again results from the electronic structure of the individual molecules. 

An applied electrical field causes an alignment of polar HF molecules. The extent of alignment depends on the magnitude of the dipole moment. 

For polycr5rstalline piezoceramics to work, the electrically charged dipoles within the entire piezoelectric component must be aligned by placing the piezoceramic within a high electric field—a process known as poling. The ability of piezoceramics to almost instantaneously convert electrical... 

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