Dielectric parameters measured in the frequency range of 10Hz to 10MHz at room temperature were shown in respective figures. The measure of the ability to store electric charge is called as Dielectric constant. Figure_____ shows the variation of dielectric constant with frequency. It is evident from the figure that with increase in frequency, the dielectric constant has decreased and finally attains constant value at higher frequency. The decrease in dielectric constant in lower frequency region is very fast and becomes slow with increase in frequency. Dielectric constant of ferrites depends upon the conduction process. The fact responsible for this conduction is hopping of electron between Fe2+ and Fe3+ . The polarization observed at grain boundaries due to local charge displacement is mainly due to this hopping of electrton. Such variation of dielectric constant with frequency in ferrites can be explained by Maxwell-Wagner model [16]. According to this model, the dielectric structure of a ferrite material is a combination of two layers. The first layer consists of large ferrite grains and acts as a conductive layer, the other with the grain boundaries that are poor conductors (offer high resistance). By hopping, the electrons heap up at the grain boundaries due to high resistance and results in polarization. This hopping …show more content…
From the figure it is evident that the value of dielectric constant increased upto x=0.03 there after the dielectric constant decreases. This increase in dielectric constant with increase in concentration of Ce3+ and Dy3+ ions may be due to the fact that the RE3+ ion introduction results in the distortion of cobalt ferrite lattice. It also results in an increase in Fe-O and RE-O bond lengths at octahedral B site resulting in an increase in polarizability with a consequent increase in dielectric constant [17,
Ewald Georg von Kleist is a German scientist who created the capacitor in November of 1745. Regrettably, Kleist did not have the proper paper work to claim in the records that the design of the capacitor was his idea. Many months later, a Dutch professor named Pieter van Musschenbroek created the Leyden jar, the world’s first capacitor (on record). It was a simple jar that was half filled with water and metal above it. A metal wire was connected to it and that wire released charges. Benjamin Franklin created his own version of the Leyden jar, the flat capacitor. This was the same experiment for the more part, but it had a flat piece of glass inside of the jar. Michael Faraday was the first scientist to apply this concept to transport electric power over a large distance. Faraday created the unit of measurement for a capacitor, called Farad.
Gadolinium and its performance were limited by the use of passive regenerators and heat exchangers in the refrigeration cycle [25]. So, a magnetic refrigeration device must utilize a regenerative process to produce a large enough temperature span to be useful for refrigeration purposes [26].
This chapter provides some insight into pulse wave analysis and its relation to arterial diseases. The shape of the arterial pulse wave is an augmentation of the forward traveling wave with the reflected wave. The amount of wave reflection is dependent on the arterial wall properties such as arterial stiffness and is expressed in terms of Augmentation Index. This approach has been studied extensively using various measuring techniques, all of which have respective advantages and disadvantages. The purpose of PWA can be seen in the section describing the medical conditions that affect the wave shape. The discussion is included to assist the reader in understanding the purpose of pulse wave analysis.
At higher frequencies, the dielectric constants are almost independent of frequency. This is because, at higher frequencies periodic reversal of the field takes place so rapidly that the charge carriers will hardly be able to orient
Schlesinger, Mordechay. "Electrochemistry Encyclopedia." Electroplating. Department of Physics, University of Windsor, Sept. 2002. Web. 17 Nov. 2013.
Polymorphism refers to the ability of the crystal to exist in different lattice structure depending on the environmental conditions. In this case, FePO4 displays two kinds of lattice structure depending on the temperature and pressure of the environment. As mentioned previously, FePO4 crystals exist in alpha-structure in low temperature and pressure and changes to beta-structure in high temperature and pressure. The temperature at which the FePO4 crystals change phase is around 980K. In the alpha structure, the tetrahedral is arranged such that the structure of the cell is trigonal and has a space group of P3221. The changes in the two symmetrically independent intertetrahedral Fe-O-P bridging angle and the correlated tilt angles is the main factor of the thermal expansion of the alpha structure. The volume and cell parameters of the alpha structure increases non-linearly as a function of temperature. The thermal expansion coefficient is found to be α (K-1) = 2.924 x 10-5 + 2.920 x 10-10 (T-300)2. As the temperature increase, the bond angles and the bond distance changes significantly especially as it increases towards the 980k where the structure will change from alpha to beta. As the temperature increase, the crystal structures realign to form the beta structure. The tetrahedral shifts such that the structure changes from trigonal to hexagonal and has a space group of p6222. It must be noted that there was no breaking of bonds and the atoms are still surrounded by the same neighbouring atoms. There is lesser symmetry in the beta structure as compared to the alpha structure. In addition, as the temperature rise, the bond distance between Fe and O in the tetrahedral actually increases, which corresponds to that of alpha quartz. This non-physical behaviour is most probably due to the increase in enthalpy of the atoms at high temperature, resulting in high amplitude and energetic vibrations. A fall in the time-averaged bond distance
The major encounters that Tesla and Faraday faced included social, economic, intellectual barriers. Considering socially, Faraday was considered to be a “...high-priest of Nature, revealing the hidden forces...”(Shortland) People saw Faraday as the highest of his field, the one who was the closest to God in relation to understanding his creation. This also shows the social standard at this point in time, many going to church and understanding when someone references a religious point. Also, for social encounters, we have Tesla with his description f what the future will be like. This was not a reaction to the society that Tesla was around, but a prediction of what they were to become. Tesla, hoping to see that people would grow to become stronger
The magnitude which depict the capability of dielectric material to retain the electric charge when it exposed to an electric field.[54] when two metal sheet is subject to electric field, one of these sheet will be negative, and the other will be positive, in this case, the dielectric material in the space between these two sheet will polarize, the dielectric constant is then represent as the ratio electric charge stored by dielectric material to that when the dielectric material is
In 1864, James Clerk Maxwell revolutionized physics by publishing A Treatise On Electricity And Magnetism (James C. Maxwell, Bio.com), in which his equations described, for the first time, the unified force of electromagnetism (Stewart, Maxwell’s Equations), and how the force would influence objects in the area around it (Dine, Quantum Field Theory). Along with other laws such as Newton’s Law Of Gravitation, it formed the area of physics called classical field theory (Classical Field Theory, Wikipedia). However, over the next century, quantum mechanics were developed, leading to the realization that classical field theory, though thoroughly accurate on a macroscopic scale, simply would not work at a quantum, or subatomic scale, due to the extremely different behaviour of elementary particles. Scientists began developing a new ideas that would describe the behaviour of subatomic particles when subjected to the fundamental forces (QFT, Columbia Electronic Dictionary)(QFT, Britannica School). Einstein’s theory of special relativity, which states that the speed of light is always constant and as a result, both space and time are, in contrary, relative, was combined into this new theory, allowing for accurate descriptions of elementary
Nikola Tesla was a Serbian American inventor, electrical engineer, mechanical engineer and physicist. He was also considered an eccentric genius and recluse. Tesla is best known for his feud with Thomas Edison over AC power Versus DC Power. He was also well known for inventing the Tesla Coil which is still used in radio technology today. Nikola Tesla was mostly forgotten until the 1990’s when there was a resurgence of interest in popular culture.
where σ is the conductivity and ε is the dielectric constant for the material. The surface resistivity of the material is
When a ray of light is bounced or reflected off of a plane surface, there is a specific law that can be used to predict the angle at which it is reflected off of the surface. This is known as the ‘Law of Reflection’ and it states:
When the generated fields pass through magnetic materials which themselves contribute internal magnetic fields, ambiguities can arise about what part of the field comes from the external currents and what comes from the material itself. It is common to define another magnetic field quantity, usually called the "magnetic field strength" designated by H. It can be defined by the relationship, H = B0/μ0 = B/μ0 – M, and has the value of unambiguously designating the driving magnetic influence from external currents in a material, independent of the material's magnetic response. The relationship for B can be written in the equivalent form, B = μ0(H + M), H and M will have the same units, amperes/meter. To further distinguish B from H, B is sometimes called the magnetic flux density or the magnetic
The Earth’s magnetic field is a major component to exploring the earth. The north and the south poles have always been a guide for travelers. Using compasses, the direction of the north pole and the south pole has always been provided by the magnetic force of the magnetic field. What many people do not know though is the earth’s magnetic field provides way more than that. The magnetic field, also known as the magnetosphere, protects us from all kinds of harmful substances. Some of these substances include solar wind and harmful radiation from the sun. The magnetosphere also protects the atmosphere, which protects us.
Humans these days take electricity for granted. We don’t truly understand what life was like without it. Most young adults will tell you their life does not depend on electricity, but they aren’t fooling anyone. They all know that their life depends on electricity; whether it’s television, their phone, Google, or the lights in their house. We need to stop taking those things for granted and give credit where credit is due. That is why I chose to write about the scientists who contributed to the discovery of electricity, which then helped modern scientists fuel the electricity phenomenons we now have today.