# How to derive Hall's coefficient for a semiconductor?

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In Technology

# Which semiconductor have positive temperature coefficient?

With the increase in temperature if the resistance increases or the current in the circuit decreases then it is said to be have positive temperature coefficient . But in semi…-conductors with the increase in temperature the electrons present in the valance band are excited and they would enter the conduction band for conduction . As the no. of charge carriers always increase in a semi-conductor , implies that the current always increases with the increase in temperature so the semi-conductor can never have positive temperature coefficient (MORE)

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# Daryl hall's lyme disease?

Musician Daryl Hall, of the pop group Hall and Oates, was diagnosed with Lyme disease in 2005. He suffered on and off with the disease for three years, but is now cured. ***I …don't know if Lyme Disease can be "cured" but he's managing it. (MORE)

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In Technology

# Why semiconductor has negative temperature coefficient of resistance?

Because if temperature of semiconductors is increased then number of free electrons per unit volume increases its conductivity increases and resistivity decreases.

# Derivative Formulas for Various Functions

Having to find the derivative of a certain function is one of the basics upon which calculus in particular, and computational mathematics in general, is based. Unfortunately, …there is no one surefire way to find the derivative of all functions. Depending on the expressions within the function, the means for obtaining the derivative of this function varies from one function to the next. In many cases, you may have to apply several different rules simultaneously in order to find the derivative of a function. This article lists some of the formulas associated with finding the derivatives of various functions.Usually, when you are first introduced to finding the derivative, the first kind of derivative that you are asked to find is the derivative of a polynomial. This polynomial usually consists of several expressions that contain a certain variable that is raised to varying powers. In order to find the derivative of a polynomial, you need to subtract the power of the variable by one, and multiply the coefficient of the polynomial term by the original power.The exponential function e the power of x is one of the most singular expressions in mathematics. The unique thing about this particular expression is that its derivative is itself. This means that whenever you obtain the derivative of e-power-x, the derivative itself will be e-power-x. It is this particular property that makes the value e, Euler's constant, a universal constant in mathematics, as well as a transcendental number.Trigonometric functions are a special class of functions in mathematics. This is because they are periodical and interrelated. This can be illustrated by the fact that the derivative of the sine function is another trigonometric function: the cosine function. It is important to note that there are no sign changes when finding the derivative of the sine function. The derivative of the function is a cosine function with the exact same sign and the exact same expression.The derivative of the cosine function is another trigonometric derivative. Unlike the derivative of the sine function, the sign is not preserved when you obtain the derivative of cosine. The derivative of cosine is negative sine. This means that when you evaluate the derivative of a cosine function, you need to flip the sign of the resulting sine function. If the sign was originally positive, it becomes negative. Likewise, if the sign was originally negative, it becomes positive.Ln(X) is one final function of interest for which you might want to find the derivative. The derivative of this function is none other than 1/X. Evaluating the value which results in 1/X using conventional means is not possible, since the number must give negative 1 when the power of the variable has 1 subtracted from it. When you multiply the original value by the coefficient, the expression evaluates to be 0, which does not compute in the traditional sense.There are almost as many different kinds of derivatives as there are functions. Some of these are very commonly used, such as the derivatives of trigonometric functions and the derivatives of exponential functions. On the other hand, there are other derivatives that are much less likely to be used, such as the derivatives of Ln(X). The most important derivatives by far that you must know if you are to derive functions correctly in mathematics are the derivatives of polynomials. These are the most commonly recurring ones, both on exams and in real-life applications.If you have time to confirm your answer, you can integrate the function for which you found the derivative. If you find that the resulting integration is the original function, then you have carried out the derivation correctly. (MORE)

In Ceramics

# The Coefficient of Expansion and Why a Potter Should Understand It

Pottery might seem like a rustic art, but there is a great deal of science behind it. Potters work with principles of physics and chemistry every time they practice their craf…t. The Coefficient of Expansion is a crucial concept to understand in order to achieve successful firing and glazing. Read more to find out what the coefficient of expansion is, how it applies to pottery, and what you need to know about it to achieve better results.The coefficient of expansion measures the degree of a material's expansion when it is heated and contraction when it is cooled. If something has a low coefficient of expansion, its size changes less when it is exposed to changes in temperature. If the coefficient is high, it changes more significantly. By changing the chemical makeup of a substance, the coefficient can be raised or lowered.Most ceramic objects expand as they are heated and contract as they are cooled. Often the body and glaze have different characteristics, but since the glaze is joined to it, it must conform to the changes in the body. It is important in pottery, then, for clay objects and their glazes to have similar coefficients of expansion. Otherwise, glaze defects will occur in the firing process.Crazing (cracks) and shivering (flaking) are two common results of mismatched coefficients of expansion between a pot and its glaze, when the two don't "fit together." These problems are not just aesthetic, either. Strength of the finished product can be compromised and so can its ability to be sanitized enough to function as dinnerware. The tension created by mismatched thermal expansion can also be enough to pull a piece apart unless a piece is glazed both inside and out.Crazing happens when a glaze has a higher expansion coefficient than the body. In other words, it not only expands more than the body when heated, it contracts more when it cools. This forces the glaze into a "too tight" fit over the body. This leads to a network of cracks. Crazing can be prevented by adjusting the "recipe" of the clay body so they both shrink at a comparable rate. Crazing can sometimes be a desired, artistic effect known as a crackle glaze.Shivering happens when the glaze doesn't contract as much as the body and it "buckles" or flakes. The end result is a glaze that looks like paint chips peeling away from the clay. This often happens on the pot's edges. In severe cases the glaze is under such compression, it can break the underlying clay body. Shivering can be corrected by adjusting the glaze recipe or the clay recipe or a combination of the two.Understanding how temperature changes clay and glaze is an important part of learning the art of pottery and ceramics. The term "coefficient of expansion" sounds scientific, but it is a principle that has been learned by potters through trial and error over thousands of years. Knowing how to mix your materials to the proper "recipe" can ensure that the coefficients are complementary. This greatly increases the number of successfully fired pieces.Even though your glaze/body coefficients match enough to survive the first test, which is cooling in a kiln, it is important the "marriage" between the body and the glaze can also withstand the heating and cooling cycles it will experience over a lifetime of use. This is why ovenware and ceramics that are "dishwasher safe" have very low coefficients of expansion and the chemical bond between the body and the glaze are precisely formulated. (MORE)

In Science

# A Brief History Covering the Invention of the Silicon Semiconductor

Most people are under the impression the silicon semiconductor is a 20th century invention. Integrated circuits such as those we use today are a product of research which star…ted as far back as 1830. Scientists began looking at a number of individual elements, along with several compounds, which would conduct an electrical current when exposed to light, yet would not conduct when heated. This allowed scientists to control the flow of electricity through these materials.During this period of research, Ferdinand Braun created the world's first non-silicon semiconductor. The Cat's Whisker diode was built from lead sulfide and a galena crystal. This arrangement allowed current to flow easily in one direction but not the other. By 1874, electricity was beginning to dominate the world. It was being used for many things, including the transmission of information via the telegraph and the telephone. By the time the early radio was invented, the term electronics had been coined, and the world would never be the same again.While the integrated circuit was still years in the future, the average "electronic" product was built using a number of vacuum tubes. These tubes were easily damaged, were very unreliable, and produced a lot of heat. They also consumed huge amounts of power to keep them working. Finally, in 1947, Bell Telephone developed an invention which would revolutionize the electronics industry. Their team of experts had developed the world's first transistor, a miniaturized version of the vacuum tube which was rugged, tiny, used very little power, and did not produce massive amounts of heat.Despite the invention of the transistor, the amount of space required to create devices with hundreds of components was still considered to be too much. The US military in particular was looking for ways to further shrink components. This led to the development of the forerunner to the modern integrated circuit, the Micro Module. This device involved creating numbers of individual modules filled with a range of components designed for a specific function. In order to build a complete system, individual modules could simply be plugged into a mainboard. While still far from perfect, this system allowed for fast reliable construction.Kilby had gone to work for Texas Instruments and was working on the development of the Micro Module. Despite its relative success, he was not convinced the device went far enough towards miniaturization to continue being effective. He began the search for a better option, and new materials he could use to shrink the components to a more practical size. In 1958 while most of the research team was away on vacation, Kilby developed the first silicon semiconductor. This first device did nothing more than produce a sine wave which could be seen on an oscilloscope, but with it the integrated circuit would be born.The effects of research by men like Kilby and Royce into the silicon semiconductor have been far reaching. Without their research and the development of the integrated circuit, many of the devices we take for granted today would not exist. From the work of Kilby came the technology needed to build computers small enough to carry with you, digital watches and a wealth of devices we have all come to rely on. Without this technology, man would never have reached the moon or developed the internet.While there is still a long way to go in the development of this technology, there will eventually be a limit to how much faster science can make it work. Eventually the speed of these devices will be limited by the speed at which electrons can flow. Another limitation faced by developers is heat generation, the more transistors which are packed into a given space, the more heat will be generated. Unless new ways to supercool them are developed, the heat will stop progress. (MORE)

# What Are Derivatives? A Financial Overview

Derivatives are often talked about in the financial news and in the wider media. Despite the widespread use of the term, these financial instruments are rarely explained in de…tail. Though seldom described, derivatives are extremely important, and hundreds of billions of dollars are exchanged buying and selling derivatives every year. Just what are derivatives, and why is it important to understand them?Defined in the broadest possible sense, derivatives are any financial instruments that derive their value from another financial instrument. This sounds somewhat confusing, but when you apply this concept to everyday situations, just what exactly derivatives are starts to make sense. Imagine that the price of corn at your local farmer's market is currently $10 a bushel, but you expect the price of corn to drop soon. With this in mind, you make an agreement with the farmer to buy 12 bushels of corn for $8 a bushel in two weeks regardless of what he is currently charging. An agreement of this sort is a derivative of corn. Specifically, it is a type of derivative called a forward contract.Derivatives are not considered to have any intrinsic value. This means that, taken on their own, derivatives do not possess any value in and of themselves. However, as all investors know, derivatives possess very significant value in financial markets. This is because they derive their value from something with intrinsic value, known as a real-valued asset. Common real-valued assets include stocks, commodities and exchange-traded funds.Theoretically, there are an infinite number of derivatives. The only limit placed on the number of possible types of derivatives is the capacity for human inventiveness. That said, there are two types of derivatives that have the most importance in worldwide financial markets: options and futures. Options are derivatives that give investors the right to buy or sell a real-valued asset for a set price before a certain date. Futures are derivatives that represent an agreement between two investors to buy and sell, respectively, a certain amount of real-valued assets by a certain date.Trading most types of derivatives is not only possible, it is widespread. Options are the most popular type of derivatives for trading with futures a close second. Trading in options requires less of an investment than trading real-valued assets. Options trading also happens much faster than asset trading, making it a good strategy for investors who enjoy making money quickly. Futures are traded in essentially the same way as options, though there are some differences. Two other types of less-common derivatives, forwards and swaps, are sometimes traded, but they are prohibited from trading in federally sanctioned exchanges.Derivatives initially seem like they are entirely in the realm of Wall Street insiders, but these financial instruments are actually quite easy to understand. Though derivatives have no intrinsic value, the value they derive from their underlying assets is often considerable. Investors who focus solely on trading derivatives have the potential to make just as much profit in the market as those who stick to real-valued assets.Options are speculative, risky derivatives. If you correctly predict the future direction of a stock price but the move does not occur before the expiration date of your option, you lose the entire amount of your investment in that option. (MORE)

In Grammar

# The Derivation of Words in the English Language

Words in the English language are governed by various rules. The morphology of words is divided into two main forms: derivation and inflection. Derivation is a set of rules th…at aid in the formation of new words from old ones, while inflection denotes the modification of a word to express the number, case, voice, person, tense, mood, or aspect. In the derivation of words, the affixes (suffixes and prefixes) are added to a root to form new words.Derivation of words is defined as the method of forming entirely new words from existing or old words by inclusion of a suffix, prefix, or compounding the word. Derivation has Latin origins with the meaning "to draw of." The prefixes in derivational words do not change the root word's class, forming a fresh noun that has a different implication. The words, "patient" and "outpatient" are good examples. In suffixes, the interpretation and the word class are both altered as in the case with "dark" and "darkness."Morphology involving derivation is usually followed with a derivational suffix or an affix, which are related to words that are lexical in nature. These words are changed into a different category. For instance, the adjective "slow" is altered to the adverb "slowly." Other derivational patterns include adjective to verb change like "modern" and "modernize," adjective to adjective as in "red" and "reddish," noun to verb like "drink" and "drinkable," verb to noun as in "write" and "writer." The derivational affixes keep the lexical meaning intact as in "write" and "rewrite." There are derivation patterns that do not undergo any change like the noun "telephone" and "to telephone." This pattern is called zero derivation or conversion. If a noun results due to derivation, it is termed as nominalization.In some situations, derivation is interspersed with other word formation types like compounding. The affixes used in derivation are termed as bound morphemes. This means that though they possess a meaning individually, they occur only when they are linked with another word. Derivation differs from word compounding in this aspect, where free morphemes are linked as in "lawsuit." Derivation also varies from inflection, which does not form new lexemes, but only new words like "table" and "tables" or "open" and "opened."Inflection involves inclusion of morphemes, which are the smallest units of a language. Derivation on the other hand denotes the addition of derivational morphemes that form new words from old ones and in some cases altering the grammatical sense. The words in dictionaries are not categorized based on inflectional morphemes, but only the derivational type. Inflection relates to regular patterns that include all members involved in a part of speech, but derivation is not so consistent.Derivation of words involves the analysis of principles that decide the new word construction irrelevant to the particular grammatical part the word has in the sentence. The derivation procedure enriches the vocabulary of a language, allowing the speakers to shift from one part of speech to another. Common derivation mistakes relate to the creation of negative words. For example, the use of "un" instead of "ir" as in "irrelevant."If a noun results due to derivation, it is termed as nominalization. For example "happy" turns into "happiness," "difficult" into "difficulty," and "refuse" into "refusal." (MORE)

In Chicago

# Chicago Pool Halls

Pool halls often bring out the best in people. Sadly, sometimes they bring out the worst as well. Chicago is known for its pool halls. These establishments are much more than …bars and much more than billiards. They represent an aged and seasoned culture unique to Chicago. If you've never been to a Chicago pool hall before, you are missing an adventure.A pool hall is a place where people go to play billiards. It is also often a bar and social meeting place. Pool halls tend to have a negative social perception. Many pool halls are primarily there for people to play pool, and nothing more, which can make for a fun atmosphere.Pool halls developed a bad reputation during the 1950s and 1960s. The reality is much calmer in most places. Chicago pool halls are known for a bit of rowdiness, but nothing too extreme. If you want to travel back in time to a world of old-fashioned billiards, you can find that in Chicago.Chris's Billiards on Milwaukee Avenue is a great place to play pool in a calmer setting. There are plenty of tables, and if you don't want to interact with people, you won't have to. This is a somewhat famous hall. It was featured in Martin Scorsese's film, "The Color of Money." Another safe option is Pressure Billiards and Cafe on Clark Street. Pressure is a modern pool hall, and is much different than most other options in Chicago. This is a great place to come relax, whether you are looking to play pool or just hang out and have a beer.Southport Lanes and Billiards on Southport Avenue is a classic Chicago pool hall with one thing different: bowling. Whether you're there for pool or for the bowling lanes, you're sure to encounter a loud and wild crowd. Marie's Golden Cue is another one of Chicago's classic halls. If you're wondering whether it's rowdy, let the sign on the front answer your questions: "We have smooth shafts and clean balls." This is a place for dedicated pool players only.Some pool halls should be avoided unless you are going specifically to play pool. Not all pool halls are family friendly, so it makes sense to read some public reviews before choosing a location. Fun can be had by all, regardless of what type of fun you desire.Chicago's pool halls are truly special. In most other American cities, pool halls have shut down or transformed into something more sedate. Only in Chicago have the pool halls of the 1950s remained much of what they were. These places can be a bit wild, but they always supply a good time.There have been many films about pool and pool halls. Most of these confront the issue of hustling. They include "The Hustler," "The Color of Money," "Poolhall Junkies," and "Shooting Gallery." (MORE)

Answered

# Why do the semiconductors have negative temperature coefficient whereas the metals have positive values?

Semiconductors: When temperature increases, more electrons jump to conduction band from valance bond. Hence resistance decreases. Metals: Already plenty of electrons are there… in conduction band. When temperature increases, the electrons in conduction band of metal vibrate and collide each other during their journey. Hence the the resistance of metal increases with increase of temperature. S.Lakshminarayana (MORE)

Updated Answer

In Technology

# What is a semiconductor?

A semiconductor is a solid whose electrical conductivity is in between that of a conductor and that of an insulator, and can be controlled over a wide range, either perm…anently or dynamically. Semiconductor materials can be elements (e.g. germanium, silicon), compounds (e.g. copper oxide, lead sulfide), or metal alloys (e.g. gallium arsenide, gallium aluminum indium phosphide). A pure semiconductor material is a very poor conductor or even an insulator, but when impurities called dopants are added it can become a quite good conductor. There are two classes of dopants: N type and P type. N type dopants create negatively charged current carriers (i.e. free electrons) in the semiconductor, just like ordinary conductors use. P type dopants create positively charged current carriers (i.e. holes) in the semiconductor. (Note: dopants do no make the semiconductor material electrically charged.) Because semiconductors have two different types of current carrier (not just the one that ordinary conductors have), it is possible to create junctions between differently doped parts of semiconductor material that conduct in one direction but not the other, or due to quantum mechanical effects do other useful things. (MORE)

Answered

In Technology

# What is negative temperature coefficient of semiconductor?

The resistance of the semiconductor material decreases with increase in temperature,this phenomenon is said to be negative temperature coefficient of semiconductor.