Before Kamerlign Onnes, in 1908, was able to liquefy helium and bring its temperature down to about 1K, it had been known that the resistance of a metal falls when cooled below room temperature. However, it was not known what value the resistance would approach if the temperature was reduced towards 0K until Onnes, while experimenting with platinum, discovered that, its resistance fell when cooled to a very low value that depended on the metal’s purity.
As the temperature of mercury was reduced toward 0K, the value of the resistance would fall smoothly until the resistance fell extremely suddenly at about 4K. Below 4K, mercury passed into a new state with electrical properties unlike those previously known: this new state that mercury had entered was called the “superconducting state.”
Superconductivity can be destroyed if a sufficiently strong magnetic field is applied. A metal in this state has very unique magnetic properties that are unlike those at normal temperatures. A superconductor is often referred to as the perfect diamagnetic. Diamagnetic, ideally, are a class of materials that do not conserve magnetic flux, but expel it. A superconductor is classified as a perfect diamagnetic because by all measurable standards the magnetic flux within the material is zero.
Electrons have a wave-like nature so an electron moving through a metal can be represented by a plane wave progressing in the same direction. A metal has a crystalline structure with the atoms lying on a repetitive lattice; a plane wave can pass through a perfectly periodic structure without being scattered into other directions. An electron is able to pass through a perfect crystal without any loss of momentum of its original direction. That is why it is important for superconductors to have very low impurities; any fault in the periodicity of the crystal will scatter the electron wave and introduce some resistance. This is called the residual resistance and it is independent of the temperature.
Thermal vibrations also increase the resistance so when the temperature is lowered, the thermal vibrations of the atoms decrease and so the electrons are less frequently scattered. In short, the resistance of a metal is dependent on the purity of a metal and its temperature: metals with few impurities reach a superconducting state at low temperatures.
The superconductivity state of a metal exists only in a certain range of temperature and field strength.
has a lower energy state. It will now tend to remain the way it is.
For the electrons that refract through the barrier, they go through a process known as quantum tunneling. Due to Heisenberg’s uncertainty principle, a wave function and Schrodinger’s equation can estimate the electron path, but instead, knowing it models the path of exponential decay, its current position is predictable with the following equation (Quantum tunneling), (Spintronics):
**thermally sensitive resistors whose prime function is to exhibit a large, predictable and precise change in electrical resistance when subjected to a corresponding change in body temperature.
Since all metals have different densities and makeups I think that the heat capacity will greatly vary. The makeup of iron is very different than aluminum so the heat capacity will be quite different. Also, a lot of metals are not completely pure and that will also have some effect on the heat capacity.
The molar specific heats of most solids at room temperature and above are nearly constant, in agreement with the Law of Dulong and Petit. At lower temperatures the specific heats drop as quantum processes become significant. The Einstein-Debye model of specific heat describes the low temperature behavior.
They can be seen as a collection of rolled sheets of graphene. CNTs demonstrate superconductivity with very large temperature transition. Electrons transport and resistance of CNTs do not depend on the sizes of CNTs. Carbon nanotubes electrodes are constructed by combining graphite powder and multiwall carbon nanotubes in a pestle and a mortar. Then, paraffin is added to the mixture by a syringe before the mixture is packed in a glass tube. After the construction, its electrochemistry is tested to verify its electro-activity by using standard solution of Fe(CN)63-/Fe(CN)64. Care is taken on information about electrode interfaces; mass transiport needs to be minimized in order to be used in catalysis, sensing and electrodeposition (Elrouby, 2013).
As the temperature increases, the movements of molecules also increase. This is the kinetic theory. When the temperature is increased the particles gain more energy and therefore move around faster. This gives the particles more of a chance with other particles and with more force.
Superconductivity, a similar phenomenon, was discovered in 1911 by Dutch physicist Heike Kamerlingh Onnes. When he cooled some mercury down to liquid helium temperatures, it began to conduct electricity with no resistance at all. People began experimenting with other metals, and found that many tranisition metals exhibit this characteristic of 0 resistance if cooled sufficiently. Superconductors are analagous to superfluids in that the charges within them move somewhat like a superfluid - with no resistance through sections of extremely small cross-sectional area. Physicists soon discovered that oxides of copper and other compounds could reach even higher superconducting temperatures. Currently, the highest temperature at wich a material can be superconductive is 138K, and is held by the compound Hg0.8Tl0.2Ba2Ca2Cu3O8.33.
Gallium? What is that? Well I will get to that but first let me tell you why I chose to research the element known as gallium. I became interested in gallium after YouTube suggested that I watch videos about gallium. Then as I watched I learned that gallium; a post-transition metal, will turn into a liquid as soon as a person touches it. Cool right? That's exactly what I thought. I found it extremely odd. Usually metals are widely known to have intense strength and can bare a lot of heat and beating. But that's not the case with gallium. And it made me really curious. So here we are now.
Temperature affects the movement of electrons in the material. When a signal voltage is passed through a wire the electrons collides with the atoms in the material. If more atoms are allowed collide with electrons, the greater the frictional resistance, which affects the cable ability to conduct (allow data to pass through the cable). Temperature causes the atoms with in the material to move. Increasing the temperature causes the atoms to “jiggle” which causes frequent collations with electrons. The opposite is true when the temperature is lowered.
This is know as resistivity. The factors I can investigate are : Ÿ Temperature Ÿ Length Ÿ Cross-sectional area/width Ÿ Material (resistivity) The factor I shall investigate is the length of a wire. Background Knowledge Resistance is when electrons travelling through the wire are impeded by the atoms within the wire. Since the electrons are charge carriers when they collide with the atoms in the wire less pass through.
Advanced materials are classified as completely new materials which have some specific properties and functions. These advance materials have large utility in daily life, hospitality, industries, sports etc. currently scientists and researchers are working and studying their specific functions etc. some great examples of these materials include thin membranes, Composite and hybrid materials, polymers, ceramic and radiation shielding composites; lightweight and nanocomposite, Metals and alloys, Ceramics, Smart materials (Photo-, thermo-, piezo-, tribo- and electro-chromic materials. Thin film coatings. Now a day thermoelectric materials have significant value in scientific world it include temperature measuring devices in furnace, energy harvestings and advance sensor etc. and many more. Here we discuss about thermoelectric and materials used in it.
The development of superconductors has been a working progress for many years and some superconductors are already in use, but there is always room for improvement. In 1911, Dutch physicist Heike Kamerlingh Onnes first discovered superconductivity when he cooled mercury to 4 degrees K (-452.47º F / -269.15º C). At this temperature, mercury’s resistance to electricity seemed to disappear. Hence, it was necessary for Onnes to come within 4 degrees of the coldest temperature that is theoretically attainable to witness the phenomenon of superconductivity. Later, in 1933 Walter Meissner and Robert Ochsenfeld discovered that a superconducting material will repel a magnetic field. A magnet moving by a conductor induces currents in the conductor, which is the principle upon which the electric generator operates. However, in a superconductor the induced currents exactly mirror the field that would have otherwise penetrated the superconducting material - causing the magnet to be repulsed- known today as the “Meissner effect.” The Meissner effect is so strong that a magnet can actually be levitated over a superconductive material, which increases the use of superconductors. After many other superconducting elements, compounds, and theories related to superconductivity were developed or discovered a great breakthrough was made. In 1986, Alex Muller and Georg Bednorz invented a ceramic substance which superconducted at the highest temperature then known: 30 K (-243.15º C). This discovery was remarkable because ceramics are normally insulators – they do not conduct electricity well. Since their discovery the highest temperature for superconductivity to occur is 138 K (-130.15º C).
There are formulas to calculate electrical conductivity and resistivity. Conductivity is defined as the inverse of resistivity (a high conductivity means a low resistance), I=V/R or current equals voltage over resistance. This is known as Ohm’s Law. Electrical resistance is calculated by the formula, R=V/I or resistance equals voltage over current. Ohm’s law however does not hold true if temperature changes. Materials that obey Ohm’s law are known as ohmic or linear because the potential difference across it varies linearly with the current. In addition, whether or not a material obeys Ohm’s law its resistance can be described in bulk resistivity. Furthermore, over sizable ranges of temperature, this temperature depe...
Toughness is the ability of a metal to mutilate plastically and to absorb energy in the process before it breaks or fracture. Metals can be heat treated to alter the properties of strength, ductility, toughness, hardness or resistance to corrosion. This can be done by using heat treatment processes which include precipitation strengthening, quenching, annealing and tempering. Annealing and tempering are the most prominent methods for treating metals. A material may become more or less brittle, harder or softer, or stronger or weaker, depending on the treatment used.