Mercury electrical resistivity

It is a white crystalline, brittle metal with a pinkish tinge. It occurs native. Bismuth is the most diamagnetic of all metals, and the thermal conductivity is lower than any metal, except mercury. It has a high electrical resistance, and has the highest Hall effect of any metal (i.e., greatest increase in electrical resistance when placed in a magnetic field). 

Contact with steel, though less harmful, may accelerate attack on aluminium, but in some natural waters and other special cases aluminium can be protected at the expense of ferrous materials. Stainless steels may increase attack on aluminium, notably in sea-water or marine atmospheres, but the high electrical resistance of the two surface oxide films minimises bimetallic effects in less aggressive environments. Titanium appears to behave in a similar manner to steel. Aluminium-zinc alloys are used as sacrificial anodes for steel structures, usually with trace additions of tin, indium or mercury to enhance dissolution characteristics and render the operating potential more electronegative. 

Superconductivity is the loss of all electrical resistance when a substance is cooled below a certain characteristic transition temperature (Ts). It is thought that the low temperatures are required to reduce the effect of the vibrations of the atoms in their crystalline lattice. Superconductivity was first observed in 1911 in mercury, for which Ts = 4 K. Over the years, many other metallic superconductors were identified, some having transition temperatures as high as 23 K. However, low-temperature superconductors need to be cooled with liquid helium, which is very expensive. To use superconducting devices on a large scale, higher transition temperatures would be required. 

The discovery of superconduction was made at Leiden University, by Heike Kamerlingh Onnes back in 1911 whilst experimenting with the electrical resistance of mercury, cooled to liquid helium temperature. His efforts were recognised with the Nobel Prise for Physics in 1913 and much later, a... 

The phenomenon of superconductivity was discovered at the beginning of the twentieth century by the Dutch physicist H. Kamerlingh Onnes, during the first attempts to liquefy helium (which at atmospheric pressure boils at 4.2 K). After refining the technique of helium liquefaction, in 1911, Onnes attempted to measure the electrical resistance of metals at these extraordinary low temperatures, and realized that at 4 K the resistance of mercury, as well as that of other metals indicated in Figure 1, became too low to be measured. This change in electrical property became the indication of the new superconductive physical state. The temperature below which materials become superconducting is defined as the critical temperature, Tc. 

Silvery metal body-centered cubic structure imparts crimson-red color to flame density 0.862g/cm3 at 20°C melts at 63.25°C density of hquid potassium at 100°C is 0.819 g/cm and 0.771g/cm3 at 300°C vaporizes at 760°C vapor pressure 123 torr at 587°C electrical resistivity 6.1 microhm-cm at 0°C and 15.31 microhm-cm at 100°C viscosity 0.25 centipoise at 250°C surface tension 86 dynes/cm at 100°C thermal neutron absorption cross section 2.07 barns reacts violently with water and acids reacts with alcohol dissolves in liquid ammonia and mercury... 

In 1908, Kamerlingh Onnes succeeded in liquefying helium, and this paved the way for many new experiments to be performed on the behaviour of materials at low temperatures. For a long time, it had been known from conductivity experiments that the electrical resistance of a metal decreased with temperature. In 1911, Onnes was measuring the variation of the electrical resistance of mercury with temperature when he was amazed to find that at 4.2 K, the resistance suddenly dropped to zero. He called this effect superconductivity and the temperature at which it occurs is known as the (superconducting) critical temperature, Tc. This effect is illustrated for tin in Figure 10.1. One effect of the zero resistance is that no power loss occurs in an electrical circuit made from a superconductor. Once an electrical current is established, it demonstrates no discernible decay for as long as experimenters have been able to watch ... 

Dilatometer. Reliable kinetic data on gamma-induced emulsion polymerization can be obtained only when the polymerization rate is measured continuously (7). The recording dilatometer used in our previous work had some disadvantages. A mercury meniscus traveled down a precision capillary, releasing a thin platinum wire within the capillary. The electrical resistance of this assembly was used as a measure for the... 

Belertser et al (1988) have observed that the electrical resistivity of amorphous chromium films at liquid-helium temperatures jumps from a value (10 3 O cm) characteristic of a poor metal by a factor 103, when the hydrogen content is increased sufficiently to increase the lattice constant by 10%. The transition is not abrupt, and is thought by these authors to be of Anderson type. They claim that it is the first time such a transition has been observed in a solid, and that it is similar to that in expanded mercury vapour (Section 4). 

Potassium and sodium are good conductors of heat.23 If the conductivity of silver be unity, that of sodium is 0 365. J. W. Hornbeck found the temp, coeff. of the thermal conductivity of potassium or sodium falls with rise of temp. The alkali metals are also good conductors of electricity 24 for example, the conductivity of sodium for heat and electricity is exceeded only by silver, copper, and gold. According to E. F. Northrup, the metals sodium, potassium, mercury, tin, lead, and bismuth have the same value for the ratio of the coeff. of electrical resistance to the coeff. of cubical expansion at the same temp. The electrical conductivity of lithium is nearly ll-4xl04 reciprocal ohms at 20°, that is, about 20 4 per cent, of the conductivity of hard silver of sodium at 2T 70, 22 4 XlO4 reciprocal ohms, that is, about 36 5 per cent, of the value of silver. 

A superconductor is a material that loses all electrical resistance below a characteristic temperature called the superconducting transition temperature, Tc. This phenomenon was discovered in 1911 by the Dutch physicist Heike Kamerlingh Onnes, who found that mercury abruptly loses its electrical resistance when it is cooled with liquid helium to 4.2 K (Figure 21.12). Below its Tc, a superconductor becomes a perfect conductor, and an electric current, once started, flows indefinitely without loss of energy. 

FIGURE 21.12 The electrical resistance of mercury falls to zero at its superconducting transition temperature,... 

Fig. 11.4.11 Electrical resistance of copper and mercury as a function of temperature.

Adsorption of mercury atoms onto thin gold film leads to scattering of conduction electrons at the gold surface resulting in an increase of surface electrical resistance. This phenomenon is used for preparation... 

Superconductivity dates back to 1911, when a Dutch physicist determined that the element mercury, when cooled to minus 452 degrees Fahrenheit, has virtually no electrical resistance. That is, it lost zero electric power when used as a means to distribute electricity from one spot to another. Two decades later, in 1933, a German physicist named Walther Meissner discovered that superconductors have no interior magnetic field. This property enabled superconductivity to be put to commercial use by 1984, when magnetic resonance imaging machines (MRIs) were commercialized for medical imaging. 

Fig. 1. Showing near zero electrical resistance at about 4.2°K for mercury (Hg) as discovered by Kamerlingh Onnes.

Quasi-reference electrodes such as platinum or silver wires or mercury pools are sometimes used in voltammetric experiments, particularly transient experiments. The advantage is low electrical resistance, but... 

Mercury has a high density (13.546 g cm" at 20 °C) and a wide liquid range (mp -38.9 °C bp 357) over most of which its volume expands uniformly. In addition, the high surface tension of mercury keeps it from sticking to glass surfaces. These properties have contributed to its use in an impressive number of laboratory applications. For a metal, mercury has an unusually high electrical resistivity or specific resistance (95.8 J,S2 cm), and this property enables it to be used as an electrical standard. Of all the common metals, only bismuth has a higher resistivity. 

Superconductivity is a phenomenon characterized by sudden and complete disappearance of electrical resistance in a substance when it is cooled below a certain tempeSrature, called the critical transition temperature, T. Superconductivity was discovered in 1911 by measuring the resistance of solid mercury (Hg) on cooling with a sharp discontinuity in resistance at about 4.2 K (see Fig. 1). In addition to the total loss... 

While Onnes was experimenting on the liquefaction of helium in 1911, he found the resistance of mercury dropped dramatically from 0.08 at 4.2 K to less than 3 x 10 Q at 4 K over a temperature interval of 0.01 K (Figure 7.1). He named this phenomenon superconductivity. This behaviour is the most striking feature of superconducting materials, in which below a critical temperature, the electrical resistance suddenly drops to effectively zero. 

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