Conductor of electricity

Semiconductors are poor conductors of electricity at low temperatures. Since the valence band is completely occupied, an applied electric field caimot change the total momentum of the valence electrons. This is a reflection of the Pauli principle. This would not be true for an electron that is excited into the conduction band. However, for a band gap of 1 eV or more, few electrons can be themially excited into the conduction band at ambient temperatures. Conversely, the electronic properties of semiconductors at ambient temperatures can be profoundly altered by the... 

Liquid ammonia, like water, is only a poor conductor of electricity. Ammonium salts dissolved in water behave as acids giving the ion NH4, whilst amides which give the ion NHj behave as bases. Thus the reaction ... 

Concentrated sulphuric acid displaces more volatile acids from their salts, for example hydrogen chloride from chlorides (see above) and nitric acid from nitrates. The dilute acid is a good conductor of electricity. It behaves as a strong dibasic acid ... 

Optical characteristics include transmitting portions of the infrared. Boron is a poor conductor of electricity at room temperature but a good conductor at high temperature. 

Zinc is a bluish-white, lustrous metal. It is brittle at ordinary temperatures but malleable at 100 to ISOoC. It is a fair conductor of electricity, and burns in air at high red heat with evolution of white clouds of the oxide. 

Lead is a bluish-white metal of bright luster, is very soft, highly malleable, ductile, and a poor conductor of electricity. It is very resistant to corrosion lead pipes bearing the insignia of Roman emperors, used as drains from the baths, are still in service. It is used in containers for corrosive liquids (such as sulfuric acid) and may be toughened by the addition of a small percentage of antimony or other metals. 

Solutions of alkah metal and ammonium iodides in Hquid iodine are good conductors of electricity, comparable to fused salts and aqueous solutions of strong acids. The Hquid is therefore a polar solvent of considerable ionising power, whereas its own electrical conductivity suggests that it is appreciably ionized, probably into I" and I (triodide). Iodine resembles water in this respect. The metal iodides and polyiodides are bases, whereas the iodine haHdes are acids. 

In ECM, electrolytes serve as conductors of electricity and Ohm s law also appHes to this type of conductor. The resistance of electrolytes may amount to hundreds of ohms. 

Aluminum is an excehent conductor of electricity, having a volume conductivity 62% of that of copper. Because of the difference in densities of the two metals, an aluminum conductor weighs only half as much as a copper conductor of equal current carrying capacity. Because of its lightness, aluminum... 

Liquid sulfur dioxide expands by ca 10% when warmed from 20 to 60°C under pressure. Pure liquid sulfur dioxide is a poor conductor of electricity, but high conductivity solutions of some salts in sulfur dioxide can be made (216). Liquid sulfur dioxide is only slightly miscible with water. The gas is soluble to the extent of 36 volumes pet volume of water at 20°C, but it is very soluble (several hundred volumes per volume of solvent) in a number of organic solvents, eg, acetone, other ketones, and formic acid. Sulfur dioxide is less soluble in nonpolar solvents (215,217,218). The use of sulfur dioxide as a solvent and reaction medium has been reviewed (216,219). 

Titanium Nitride. Titanium nitride [25583-20-4] has the cubic NaCl stmeture, but the stmeture is stable over a wide range of either anion or cation deficiency (TINq 25 = 421 pm TiN q, = 423.5 pm). The nitride is a better conductor of electricity than titanium metal. It becomes... 

The fundamental parameters in the two main methods of achieving ignition are basically the same. Recent advances in the field of combustion have been in the development of mathematical definitions for some of these parameters. For instance, consider the case of ignition achieved by means of an electric spark, where electrical energy released between electrodes results in the formation of a plasma in which the ionized gas acts as a conductor of electricity. The electrical energy Hberated by the spark is given by equation 2 (1), where V = the potential, V 7 = the current. A 0 = the spark duration, s and t = time, s. 

Aluminium and copper conductors start oxidizing at about 90°C. The oxides of aluminium (AI2O) and copper (CuO) are poor conductors of electricity. They may adversely affect bus conductors, particularly at joints, and reduce their current-carrying capacity over time, and lead to their overheating, even to an eventual failure. Universal practice therefore is to restrict the operating temperature... 

Electronic conductivity Flexible conductor of electricity heating elements (resistance heating), shielding of electromagnetic radiation field flattening (high-voltage cables), materials with antistatic capability... 

Many metal sulfides have important physical properties.They range from insulators, through semiconductors to metallic conductors of electricity, and some are even superconductors. 

As expected from their structures, the elements are poor conductors of electricity solid F2 and CI2 have negligible conductivity and Br2 has a value of 5 X 10 ohm cm just below the mp. Iodine single crystals at room temperature have a conductivity of 5 x 10 ohm cm perpendicular to the be layer plane but this increases to 1.7 x 10 ohm cm" within this plane indeed, the element is a two-dimensional semiconductor with a band gap g 1.3eV (125kJmol" ). Even more remarkably, when crystals of iodine are compressed they become metallic, and at 350kbar have a conductivity of 10" ohm" cm", The metallic nature of the conductivity is confirmed by its negative temperature coefficient. 

Ionic compounds in solution and in molten state are good conductors of electricity. Melts and solutions of covalent substances are nonconducting. Inorganic substances rarely undergo combustion, whereas (organic) covalent compounds do so readily. 

Water is a very poor conductor of electricity. Yet when sodium chloride dissolves in water, the solution conducts readily. The dissolved sodium chloride must be responsible. How does the dissolved salt permit charge to move through the liquid One possibility is that when salt dissolves in water, particles with electric charge are produced. The movement of these charged particles through the solution accounts for the current. Salt has the formula, NaCl—for every sodium atom there is one chlorine atom. Chemists have... 

All the alkalies are metals in their elementary states. When the metal surfaces are clean, they have a bright, silvery luster. The metals are excellent conductors of electricity and heat. They are soft and malleable, and have low melting points (compared with almost all other elementary metals). 

Looking at a sample of each transition element in the fourth row, we see that they are all metallic. When clean, they are shiny and lustrous. They are good conductors of electricity and also of heat some of them (copper, silver, gold) are quite outstanding in these respects. One of them (mercury) is ordinarily a liquid all others are solids at room temperature. 

Aqueous solutions of many salts, of the common strong acids (hydrochloric, nitric and sulphuric), and of bases such as sodium hydroxide and potassium hydroxide are good conductors of electricity, whereas pure water shows only a very poor conducting capability. The above solutes are therefore termed electrolytes. On the other hand, certain solutes, for example ethane-1,2-diol (ethylene glycol) which is used as antifreeze , produce solutions which show a conducting capability only little different from that of water such solutes are referred to as non-electrolytes. Most reactions of analytical importance occurring in aqueous solution involve electrolytes, and it is necessary to consider the nature of such solutions. 

In the nonlinear systems, one often encounters subharmonics that have frequencies lower than that of the fundamental wave. As an example, consider a nonlinear conductor of electricity such as an electron tube circuit in which there exists between the anode current ia and the grid voltage v, a relation of the form... 

FIGURE 1.4 Pure water is a poor conductor of electricity, as shown by the very dim glow ot the bulb in the circuit on the left (a). However, when ions arc present, as in an electrolyte solution, the solution does conduct. The ability of the solution to conduct is low when the solute is a weak electrolyte (b) but significant when the solute is a strong electrolyte (c), even when the solute concentration is the same in each instance. 

The concentrations of H30 + and OH are very low in pure water, which explains why pure water is such a poor conductor of electricity. To imagine the very tiny extent of autoprotolysis, think of each letter in this book as a water molecule. We would need to search through more than 50 books to find one ionized water molecule. The autoprotolysis reaction is endothermic (AH° = +56 kj-mol l), and so we can expect Kw to increase with temperature, and aqueous solutions to have higher concentrations of both hydronium and hydroxide ions at higher temperatures. Unless otherwise stated, all the calculations in this chapter will be for 25°C. 

In diamond, carbon is sp hybridized and forms a tetrahedral, three-dimensional network structure, which is extremely rigid. Graphite carbon is sp2 hybridized and planar. Its application as a lubricant results from the fact that the two-dimensional sheets can slide across one another, thereby reducing friction. In graphite, the unhybridized p-electrons are free to move from one carbon atom to another, which results in its high electrical conductivity. In diamond, all electrons are localized in sp3 hybridized C—C cr-bonds, so diamond is a poor conductor of electricity. 

Alloys are usually (1) harder and more brittle, and (2) poorer conductors of electricity than the metals from which they are made. 

An electric current can be defined as a flow of electrons. In conductors, such as metals, the attraction between the outer electrons and the nucleus of the atom is weak, the outer electrons can move readily and consequently metals are good conductors of electricity. In other materials, electrons are strongly bonded to the nucleus and are not free to move. Such materials are insulators (or dielectrics). In semiconductors, the conductivity falls between those of conductors and insulators. Table 13.1 lists the characteristics of all three groups. 

Describe what is necessary for a substance to be a conductor of electricity. 

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