Conducting wires

Diffusion in the bulk crystals may sometimes be short circuited by diffusion down grain boundaries or dislocation cores. The boundary acts as a planar channel, about two atoms wide, with a local diffusion rate which can be as much as 10 times greater than in the bulk (Figs. 18.8 and 10.4). The dislocation core, too, can act as a high conductivity wire of cross-section about (2b), where b is the atom size (Fig. 18.9). Of course, their contribution to the total diffusive flux depends also on how many grain boundaries or dislocations there are when grains are small or dislocations numerous, their contribution becomes important. 

Kelvin effect The electrical potential gradient caused by a temperature gradient along a conducting wire. Also known as the Thomson Effect. 

The factors that are of importance in the enhancement of the corrosion rate of one metal when it is in direct electronic contact with another (c/. cathodic protection where contact is by conducting wire) are as follows. 

The unit of electrical potential is the volt (V) which is the difference of potential between two points of a conducting wire which carries a constant... 

Electrical conductance probes These can be either flush probes or wire probes. Flush probes are imbedded in a nonconducting wall, with one electrode connected to a voltage source and the second through a precision resistor to ground (Telles and Dukler, 1970 Chu and Dukler, 1974). Wire probes use closely spaced, nearly parallel conducting wires of small diameter, which are positioned normal to the flow (Brown et al., 1978). 

Bridges give a mean resistance value around 7 = 0. Strictly, they should be used only for linear components. In both cases (d.c. or a.c.), the resistance measurements are made in four-wire configuration, since the resistor to be measured is at low temperature whereas the measuring instrument is at room temperature the electric connection is usually made by low thermal conductivity wires which are also poor electrical conductors (remind the Wiedeman-Franz law). 

The voltage difference between two conductive materials is reduced to zero by bonding the two materials, that is, by bonding one end of a conducting wire to one of the materials and bonding the other end to the second material. 

An electrochemical cell which spontaneously produces current (or energy) when the electrodes are connected externally by a conducting wire. 

Several reports concerning the development of stable and rugged sheathless interfaces were proposed. The first sheathless interface was developed by Olivares et al., and two types of sheathless interfaces are currently distinguished. The first one consists of a nanospray needle, which is inserted with a connection unit to the CE capillary. This setup allows changing the spray needle alone independently on the capillary exchange.The second approach involves the use of the end of capillary tip as an emitter with the help of a capillary-outlet conductive coating " or by inserting a conductive wire into the capillary outlet. 

What is the current density in an extension cord used for a 100-W table lamp Assume that the copper conducting wire in the cord is 1 mm in diameter and the voltage is 110 V. Express your result in A/cm as well as in A/m (compare to the values in Table 12.1). 

Have you ever wondered how a battery works You can find out how in this chapter. In Chapter 11, you learned how oxidation-reduction reactions transfer electrons from one species to another. Batteries use oxidation-reduction reactions, but they are carefully designed so the flow of electrons takes place through a conducting wire. The first battery was made in 1796 by Alessandro Volta, and batteries are commonly called voltaic cells in his honor. There are many different ways to construct a voltaic cell, but in all cases, two different chemical species must be used. The voltage of the cell depends on which species are used. 

The search for flexible, noncorrosive, inexpensive conductive materials has recently focused on polymeric materials. This search has increased to include, for some applications, nanosized fibrils and tubes. The conductivity of common materials is given in Figure 19.1. As seen, most polymers are nonconductive and, in fact, are employed in the electronics industry as insulators. This includes PE and PVC. The idea that polymers can become conductive is not new and is now one of the most active areas in polymer science. The advantages of polymeric conductors include lack of corrosion, low weight, ability to lay wires on almost a molecular level, and ability to run polymeric conductive wires in very intricate and complex designs. The topic of conductive carbon nanotubes has already been covered (Section 12.17). 

Communication networks that relay changes detected by the sensor components through fiberoptics or conductive wire ... 

In the sheathless interface, the electrical contact is obtained by coating with either a metal [85, 88-90] or a conductive polymer [91] the separation capillary outlet, which is shaped as sharp tip. Also employed are sheathless interfaces in which the electrical contact is established using a metal electrode or a conductive wire inserted into the outlet of the separation capillary [92], A small gap between the separation capillary and the needle of the ionization device filled by a liquid is the approach made to establish the electrical contact in the liquid junction interface [86,87], This arrangement is also realized by making porous through chemical etching the tip [93] or a small section of the wall [94] of the separation capillary at its outlet. 

Using scanning probe microscope one can follow the manipulation process. For instance, the nanotweezers were shown to be able to grab and pick up clusters or nanowires with diameter of 500 nm. Moreover, one can immediately probe their electrical properties, since the tweezer arms serve as conducting wires. The probing may not be limited to manmade materials but it can also be used to manipulate and modify substructures within cells once the nanowire tips will be insulated. 

Finally, it is always possible to make DNA a conducting wire by coating it with silver or other metal, as done by Braun et al. [8]. The trick would be to do this while retaining the self-assembly properties of DNA. Alternatively, one could make use of the self-assembly properties before carrying out the coating, as done by Braun et al. 

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