CRACK-STONE

CRACK-STOONE is a non explosive demolition agent which is mainly used for dimolishing of Rock and Concrete.

crack- stone is quite different from ordinary demolition materiaals such as explosives and dangerous materials.
FEATURES OF CRACK-STONE

* NO NOICE
* NO FIYROCK
* NO GROUND VIBRATION
* NO DUST
* NO ENVIRONMNENTAL POLLUTION

ADVANTAGES OF CRACK-STONE

^ NO. LICENSE OR PERMIT REQUIRED
^ EASY TO USED.NO SPECIALIZED KNOWLEDGE IS REQUIRED
^ MSDS (material safety date sheet) AVAILABLE


USED OF CRACK-STONE
@ Breaking Rock & Boulders in to pieces
@ Demolition of Concrete & concrete structures
@ demolishing of Reinforced concrete]
@ Slabbing of marbls,granite,lime stone, sand stone
@ used in following civil Engineering fields

# Bridges
# Machinery Bases
# Dams
# concrete piers
# Slabs 6" thick or more

contact....
jkbasha@gmail.com
5Kg bag 12$ only

Steel

Steel is an alloy consisting mostly of iron, with a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten. Carbon and other elements act as a hardening agent, preventing dislocations in the iron atom crystal lattice from sliding past one another. Varying the amount of alloying elements and form of their presence in the steel (solute elements, precipitated phase) controls qualities such as the hardness, ductility, and tensile strength of the resulting steel. Steel with increased carbon content can be made harder and stronger than iron, but is also less ductile.
Alloys with a higher carbon content are known as cast iron because of their lower melting point and castability. Steel is also distinguished from wrought iron, which can contain a small amount of carbon, but it is included in the form of slag inclusions. Two distinguishing factors are steel's increased rust resistance and better weldability.
Though steel had been produced by various inefficient methods long before the Renaissance, its use became more common after more efficient production methods were devised in the 17th century. With the invention of the Bessemer process in the mid-19th century, steel became an inexpensive mass-produced material. Further refinements in the process, such as basic oxygen steelmaking, further lowered the cost of production while increasing the quality of the metal. Today, steel is one of the most common materials in the world, with more than 1300 million tons produced annually. It is a major component in buildings, infrastructure, tools, ships, automobiles, machines, appliances, and weapons. Modern steel is generally identified by various grades of steel defined by various standards organizations.

Transformer

Pole-mounted single-phase transformer with center-tapped secondary (note use of grounded conductor, right, as one leg of the primary feeder)
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core, and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the secondary winding. This effect is called mutual induction.
If a load is connected to the secondary, an electric current will flow in the secondary winding and electrical energy will be transferred from the primary circuit through the transformer to the load. In an ideal transformer, the induced voltage in the secondary winding (VS) is in proportion to the primary voltage (VP), and is given by the ratio of the number of turns in the secondary (NS) to the number of turns in the primary (NP) as follows:

By appropriate selection of the ratio of turns, a transformer thus allows an alternating current (AC) voltage to be "stepped up" by making NS greater than NP, or "stepped down" by making NS less than NP.
In the vast majority of transformers, the windings are coils wound around a ferromagnetic core, air-core transformers being a notable exception.
Transformers range in size from a thumbnail-sized coupling transformer hidden inside a stage microphone to huge units weighing hundreds of tons used to interconnect portions of power grids. All operate with the same basic principles, although the range of designs is wide. While new technologies have eliminated the need for transformers in some electronic circuits, transformers are still found in nearly all electronic devices designed for household ("mains") voltage. Transformers are essential for high voltage power transmission, which makes long distance transmission economically practical.

Tachogenerator

Tachogenerators are frequently used to power tachometers to measure the speeds of electric motors, engines, and the equipment they power. Generators generate voltage roughly proportional to shaft speed. With precise construction and design, generators can be built to produce very precise voltages for certain ranges of shaft speeds

Linear electric generator

In the simplest form of linear electric generator, a sliding magnet moves back and forth through a solenoid - a spool of copper wire. An alternating current is induced in the loops of wire by Faraday's law of induction each time the magnet slides through. This type of generator is used in the Faraday flashlight. Larger linear electricity generators are used in wave power schemes.

Terminology

Rotor from generator at Hoover Dam, United States
The two main parts of a generator or motor can be described in either mechanical or electrical terms:
Mechanical:
• Rotor: The rotating part of an electrical machine
• Stator: The stationary part of an electrical machine
Electrical:
• Armature: The power-producing component of an electrical machine. In a generator, alternator, or dynamo the armature windings generate the electrical current. The armature can be on either the rotor or the stator.
• Field: The magnetic field component of an electrical machine. The magnetic field of the dynamo or alternator can be provided by either electromagnets or permanent magnets mounted on either the rotor or the stator.
Because power transferred into the field circuit is much less than in the armature circuit, AC generators nearly always have the field winding on the rotor and the stator as the armature winding. Only a small amount of field current must be transferred to the moving rotor, using slip rings. Direct current machines necessarily have the commutator on the rotating shaft, so the armature winding is on the rotor of the machine.

MHD generator

A magnetohydrodynamic generator directly extracts electric power from moving hot gases through a magnetic field, without the use of rotating electromagnetic machinery. MHD generators were originally developed because the output of a plasma MHD generator is a flame, well able to heat the boilers of a steam power plant. The first practical design was the AVCO Mk. 25, developed in 1965. The U.S. government funded substantial development, culminating in a 25 MW demonstration plant in 1987. In the Soviet Union from 1972 until the late 1980s, the MHD plant U 25 was in regular commercial operation on the Moscow power system with a rating of 25 MW, the largest MHD plant rating in the world at that time. MHD generators operated as a topping cycle are currently (2007) less efficient than combined-cycle gas turbines

Faraday's disk

In the years of 1831-1832 Michael Faraday discovered the operating principle of electromagnetic generators. The principle, later called Faraday's law, is that a potential difference is generated between the ends of an electrical conductor that moves perpendicular to a magnetic field. He also built the first electromagnetic generator, called the 'Faraday disk', a type of homopolar generator, using a copper disc rotating between the poles of a horseshoe magnet. It produced a small DC voltage.
This design was inefficient due to self-cancelling counterflows of current in regions not under the influence of the magnetic field. While current flow was induced directly underneath the magnet, the current would circulate backwards in regions outside the influence of the magnetic field. This counterflow limits the power output to the pickup wires, and induces waste heating of the copper disc. Later homopolar generators would solve this problem by using an array of magnets arranged around the disc perimeter to maintain a steady field effect in one current-flow direction.
Another disadvantage was that the output voltage was very low, due to the single current path through the magnetic flux. Experimenters found that using multiple turns of wire in a coil could produce higher more useful voltages. Since the output voltage is proportional to the number of turns, generators could be easily designed to produce any desired voltage by varying the number of turns. Wire windings became a basic feature of all subsequent generator designs.
However, recent advances (rare earth magnets) have made possible homo-polar motors with the magnets on the rotor, which should offer many advantages to

genarator Historical developments

Before the connection between magnetism and electricity was discovered, electrostatic generators were invented that used electrostatic principles. These generated very high voltages and low currents. They operated by using moving electrically charged belts, plates and disks to carry charge to a high potential electrode. The charge was generated using either of two mechanisms:
• Electrostatic induction
• The triboelectric effect, where the contact between two insulators leaves them charged.
Because of their inefficiency and the difficulty of insulating machines producing very high voltages, electrostatic generators had low power ratings and were never used for generation of commercially-significant quantities of electric power. The Wimshurst machine and Van de Graaff generator are examples of these machines that have survived

Electrical generator

In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. The reverse conversion of electrical energy into mechanical energy is done by a motor; motors and generators have many similarities. A generator forces electrons in the windings to flow through the external electrical circuit. It is somewhat analogous to a water pump, which creates a flow of water but does not create the water inside. The source of mechanical energy may be a reciprocating or turbine steam engine, water falling through a turbine or waterwheel, an internal combustion engine, a wind turbine, a hand crank, compressed air or any other source of mechanical energy.

Auto cad Version history

Official Name Release Date of release Comments


AutoCAD Version 1.0 1 1982, December DWG R1.0 file format introduced.

AutoCAD Version 1.2 2 1983, April DWG R1.2 file format introduced.

AutoCAD Version 1.3 3 1983, August

AutoCAD Version 1.4 4 1983, October DWG R1.4 file format introduced.

AutoCAD Version 2.0 5 1984, October DWG R2.05 file format introduced.

AutoCAD Version 2.1 6 1985, May DWG R2.1 file format introduced.

AutoCAD Version 2.5 7 1986, June DWG R2.5 file format introduced.

AutoCAD Version 2.6 8 1987, April DWG R2.6 file format introduced. Last version to run without a math co-processor.

AutoCAD Release 9 9 1987, September DWG R9 file format introduced.

AutoCAD Release 10 10 1988, October DWG R10 file format introduced.

AutoCAD Release 11 11 1990, October DWG R11 file format introduced.

AutoCAD Release 12 12 1992, June DWG R11/R12 file format introduced. Last release for Apple Macintosh.

AutoCAD Release 13 13 1994, November DWG R13 file format introduced. Last release for Unix, MS-DOS and Windows 3.11.

AutoCAD Release 14 14 1997, February DWG R14 file format introduced.

AutoCAD 2000 15.0 1999, March DWG 2000 file format introduced.

AutoCAD 2000i 15.1 2000, July

AutoCAD 2002 15.2 2001, June

AutoCAD 2004 16.0 2003, March DWG 2004 file format introduced.

AutoCAD 2005 16.1 2004, March

AutoCAD 2006 16.2 2005, March

AutoCAD 2007 17.0 2006, March DWG 2007 file format introduced.

AutoCAD 2008 17.1 2007, March Annotative Objects introduced. First release for the x86-64 versions of Windows XP and Vista.

AutoCAD 2009 17.2 2008, March Revisions to the user interface including the option of a Microsoft Office 2007-like tabbed ribbon.

AutoCAD 2010 18.0 2009, March 24 DWG 2010 file format introduced. Parametrics introduced. Mesh 3D solid modeling introduced. Both 32-bit and 64-bit versions of AutoCAD 2010 and AutoCAD LT 2010 are compatible with and supported under Microsoft Windows 7.

AutoCAD 2011 18.1 2010, March 25 Surface Modeling, Surface Analysis and Object Transparency introduced.

Cad File formats

AutoCAD's native file format, DWG, and to a lesser extent, its interchange file format, DXF, have become de facto standards for CAD data interoperability. AutoCAD in recent years has included support for DWF, a format developed and promoted by Autodesk for publishing CAD data. In 2006, Autodesk estimated the number of active DWG files to be in excess of one billion.


In the past, Autodesk has estimated the total number of DWG files in existence to be more than three billion.

Auto cad Vertical programs

Autodesk has also developed a few vertical programs, for discipline-specific enhancements. AutoCAD Architecture (formerly Architectural Desktop), for example, permits architectural designers to draw 3D objects such as walls, doors and windows, with more intelligent data associated with them, rather than simple objects such as lines and circles. The data can be programmed to represent specific architectural products sold in the construction industry, or extracted into a data file for pricing, materials estimation, and other values related to the objects represented. Additional tools allow designers to generate standard 2D drawings, such as elevations and sections, from a 3D architectural model. Similarly, Civil Design, Civil Design 3D, and Civil Design Professional allow data-specific objects to be used, allowing standard civil engineering calculations to be made and represented easily. AutoCAD Electrical, AutoCAD Civil 3D, AutoCAD Map 3D, AutoCAD Mechanical, AutoCAD MEP, AutoCAD P&ID, AutoCAD Plant 3D and AutoCAD Structural Detailing are other examples of industry-specific CAD applications built on the AutoCAD platform

Auto cad Student versions

AutoCAD is licensed at a significant discount over commercial retail pricing to qualifying students and teachers, with both a 14 month and perpetual license available. The student version of AutoCAD is functionally identical to the full commercial version, with one exception: DWG files created or edited by a student version have an internal bit-flag set (the "educational flag"). When such a DWG file is printed by any version of AutoCAD (commercial or student), the output will include a plot stamp / banner on all four sides. Objects created in the Student Version cannot be used for commercial use. These Student Version objects will 'infect' a commercial version DWG file if imported[


The Autodesk student community provides registered students with free access to different Autodesk applications

AutoCAD Freestyle

Built on the AutoCAD platform, AutoCAD Freestyle is a simplified, low-cost (US$149) application that makes it easy to create accurate, professional-looking 2D drawings and sketches

AutoCAD LT

AutoCAD LT is a lower cost version of AutoCAD with reduced capabilities first released in November 1993. AutoCAD LT, priced at $495, became the first product in the company's history priced below $1000 to bear the name 'AutoCAD'. In addition to being sold directly by Autodesk, it can also be purchased at computer stores, unlike the full version of AutoCAD which must be purchased from official Autodesk dealers. Autodesk developed AutoCAD LT so that they would have an entry-level CAD package to compete in the lower price level.

AutoCAD Origin

AutoCAD was derived from a program called Interact, which was written in a proprietary language (SPL) and ran on the Marinchip Systems 9900 computer (Marinchip was owned by Autodesk co-founders John Walker and Dan Drake.)


When Marinchip Software Partners (later to be renamed Autodesk) was formed, they decided to re-code Interact in C and PL/1 -- C, because it seemed to be the biggest upcoming language, and PL/1. In the end, the PL/1 version was unsuccessful. The C version was, at the time, one of the most complex program in that language to date. Autodesk even had to work with the compiler developer (Lattice) to fix certain limitations to get AutoCAD to run.

AutoCAD

AutoCAD is a CAD (Computer Aided Design or Computer Aided Drafting) software application for 2D and 3D design and drafting. It was developed and sold by Autodesk, Inc. First released in December 1982, AutoCAD was one of the first CAD programs to run on personal computers, notably the IBM PC. At that time, most other CAD programs ran on mainframe computers or mini-computers which were connected to a graphics computer terminal for each user.


Early releases of AutoCAD used primitive entities — lines, polylines, circles, arcs, and text — to construct more complex objects. Since the mid-1990s, AutoCAD has supported custom objects through its C++ Application Programming Interface (API). Modern AutoCAD includes a full set of basic solid modeling and 3D tools. With the release of AutoCAD 2007 came improved 3D modeling, which meant better navigation when working in 3D. Moreover, it became easier to edit 3D models. The mental ray engine was included in rendering, it was now possible to do quality renderings. AutoCAD 2010 introduced parametric functionality and mesh modeling.

AutoCAD supports a number of APIs for customization and automation. These include AutoLISP, Visual LISP, VBA, .NET and ObjectARX. ObjectARX is a C++ class library, which was also the base for products extending AutoCAD functionality to specific fields, to create products such as AutoCAD Architecture, AutoCAD Electrical, AutoCAD Civil 3D, or third-party AutoCAD-based applications.

Currently, AutoCAD only runs under Microsoft Windows operating systems. It is available in 32-bit and in native 64-bit versions. Versions for Unix and Mac OS were released in the 1980s and 1990s, but these were later dropped. AutoCAD can run on an emulator or compatibility layer like VMware Workstation or Wine, albeit subject to various performance issues that can often arise when working with 3D objects or large drawings.

AutoCAD and AutoCAD LT are available for English, German, French, Italian, Spanish, Japanese, Korean, Chinese Simplified, Chinese Traditional, Russian, Czech, Polish, Hungarian, Brazilian, Portuguese, Danish, Dutch, Swedish, Finnish, Norwegian, and Vietnamese. The extent of localization varies from full translation of the product to documentation only. The AutoCAD command set is localized as a part of the software localization.

Electrolytic capacitor

An electrolytic capacitor is a type of capacitor that uses an electrolyte, an ionic conducting liquid, as one of its plates, to achieve a larger capacitance per unit volume than other types. They are often referred to in electronics usage simply as "electrolytics". They are used in relatively high-current and low-frequency electrical circuits, particularly in power supply filters, where they store charge needed to moderate output voltage and current fluctuations in rectifier output. They are also widely used as coupling capacitors in circuits where AC should be conducted but DC should not. There are two types of electrolytics; aluminum and tantalum.

Electrolytic capacitors are capable of providing the highest capacitance values of any type of capacitor. However they have drawbacks which limit their use. The voltage applied to them must be polarized; one specified terminal must always have positive potential with respect to the other. Therefore they cannot be used with AC signals without a DC bias. They also have very low breakdown voltage, higher leakage current and inductance, poorer tolerances and temperature range, and shorter lifetimes compared to other types of capacitors.

History

There is no clear inventor of the electrolytic capacitor. It is one of the many technologies that spent many years as a laboratory curiosity, a classic "solution looking for a problem".

The principle of the electrolytic capacitor was discovered in 1886 by Charles Pollak, as part of his research into anodizing of aluminum and other metals. Pollack discovered that due to the thinness of the aluminum oxide layer produced, there was a very high capacitance between the aluminum and the electrolyte solution. A major problem was that most electrolytes tended to dissolve the oxide layer again when the power is removed, but he eventually found that sodium perborate (borax) would allow the layer to be formed and not attack it afterwards. He was granted a patent for the borax-solution aluminum electrolytic capacitor in 1897.

The first application of the technology was in making starting capacitors for single-phase alternating current (AC) motors. Although most electrolytic capacitors are polarized, that is, they can only be operated with direct current (DC), by separately anodizing aluminum plates and then interleaving them in a borax bath, it is possible to make a capacitor that can be used in AC systems.

Nineteenth and early twentieth century electrolytic capacitors bore little resemblance to modern types, their construction being more along the lines of a car battery. The borax electrolyte solution had to be periodically topped up with distilled water, again reminiscent of a lead acid battery.

The first major application of DC versions of this type of capacitor was in large telephone exchanges, to reduce relay hash (noise) on the 48 volt DC power supply. The development of AC-operated domestic radio receivers in the late 1920s created a demand for large capacitance (for the time) high voltage capacitors, typically at least 4 microfarads and rated at around 500 volts DC. Waxed paper and oiled silk capacitors were available but devices with that order of capacitance and voltage rating were bulky and prohibitively expensive.

The ancestor of the modern electrolytic capacitor was patented by Julius Lilienfeld in 1926. Lilienfeld's design resembled that of a silver mica capacitor, but with electrolyte-soaked paper sheets in place of the mica dielectric. However, it proved impractical to adequately seal the devices, and in the hot conditions inside typical mains-operated radio receivers the capacitors quickly dried out and failed.

Retired US Navy engineer Ralph D. Mershon is credited with developing the first commercially available "radio" electrolytic capacitor that was used in any quantity (although other researchers produced broadly similar devices). The "Mershon Condenser" as it was known (condenser was the earlier term for capacitor) was constructed like a conventional paper capacitor, with two long strips of aluminum foil interwound with strips of insulating paper, but with the paper saturated with electrolyte solution instead of wax. Rather than trying to hermetically seal the devices, Mershon's solution was to simply fit the capacitor into an oversize aluminum or copper can, half-filled with extra electrolyte. These units are referred to as "wet electrolytics," and those with liquid still inside are prized by vintage radio collectors.

"Mershons" were an immediate success and the name "Mershon Condenser" was, for a short time, synonymous with quality radio receivers in the late 1920s. However, due to a number of manufacturing difficulties, their service life turned out to be quite short and Mershon's company went bankrupt in the early 1930s.

It was not until World War II, when sufficient resources were finally applied to finding the causes of electrolytic capacitor unreliability, that they started to become as reliable as they are today. A major advance was the process of etching and pre-anodizing the foil prior to assembly, which allowed the use of much less corrosive electrolyte solutions, which in turn meant the devices could be left unenergized for long periods without deterioration. Modern electrolytic capacitors can remain usable after lying idle for decades, whereas the original Mershons could not tolerate more than a few months without a polarizing voltage. Elaborate "re-forming" procedures were necessary to avoid damage to receivers that had not been used for some tim

: History of the transistor

Assorted discrete transistors. Packages in order from top to bottom: TO-3, TO-126, TO-92, SOT-23

A transistor is a semiconductor device used to amplify and switch electronic signals. It is made of a solid piece of semiconductor material, with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals. Because the controlled (output) power can be much more than the controlling (input) power, the transistor provides amplification of a signal. Today, some transistors are packaged individually, but many more are found embedded in integrated circuits.

The transistor is the fundamental building block of modern electronic devices, and its presence is ubiquitous in modern electronic systems. Following its release in the early 1950s the transistor revolutionised the field of electronics, and paved the way for smaller and cheaper radios, calculators, and computers, amongst other things.
Main article: History of the transistor

A replica of the first working transistor.

Physicist Julius Edgar Lilienfeld filed the first patent for a transistor in Canada in 1925, describing a device similar to a Field Effect Transistor or "FET".[1] However, Lilienfeld did not publish any research articles about his devices,[citation needed] nor did his patent cite any examples of devices actually constructed. In 1934, German inventor Oskar Heil patented a similar device.[2]

In 1947, John Bardeen and Walter Brattain at AT&T's Bell Labs in the United States observed that when electrical contacts were applied to a crystal of germanium, the output power was larger than the input. Solid State Physics Group leader William Shockley saw the potential in this, and over the next few months worked to greatly expand the knowledge of semiconductors, and thus could be described as the "father of the transistor". The term was coined by John R. Pierce.[3] According to physicist/historian Robert Arns, legal papers from the Bell Labs patent show that William Shockley and Gerald Pearson had built operational versions from Lilienfeld's patents, yet they never referenced this work in any of their later research papers or historical articles.[4]

The name 'transistor' is a portmanteau of the term 'transfer resistor'.[5]

The first silicon transistor was produced by Texas Instruments in 1954.[6] This was the work of Gordon Teal, an expert in growing crystals of high purity, who had previously worked at Bell Labs.[7] The first MOS transistor actually built was by Kahng and Atalla at Bell Labs in 1960.[8]

Printed circuit board (p.c.b)

(Part of a 1983 Sinclair ZX Spectrum computer board; a populated PCB, showing the conductive traces, vias (the through-hole paths to the other surface), and some mounted electrical components)

A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board (PWB) or etched wiring board. A PCB populated with electronic components is a printed circuit assembly (PCA), also known as a printed circuit board assembly (PCBA).


PCBs are inexpensive, and can be highly reliable. They require much more layout effort and higher initial cost than either wire-wrapped or point-to-point constructed circuits, but are much cheaper and faster for high-volume production. Much of the electronics industry's PCB design, assembly, and quality control needs are set by standards that are published by the IPC organization



History

The inventor of the printed circuit was the Austrian engineer Paul Eisler (1907–1995) who, while working in England, made one circa 1936 as part of a radio set. Around 1943 the USA began to use the technology on a large scale to make rugged radios for use in World War II. After the war, in 1948, the USA released the invention for commercial use. Printed circuits did not become commonplace in consumer electronics until the mid-1950s, after the Auto-Sembly process was developed by the United States Army.


Before printed circuits (and for a while after their invention), point-to-point construction was used. For prototypes, or small production runs, wire wrap or turret board can be more efficient. Predating the printed circuit invention, and similar in spirit, was John Sargrove's 1936-1947 Electronic Circuit Making Equipment (ECME) which sprayed metal onto a Bakelite plastic board. The ECME could produce 3 radios per minute.


Originally, every electronic component had wire leads, and the PCB had holes drilled for each wire of each component. The components' leads were then passed through the holes and soldered to the PCB trace. This method of assembly is called through-hole construction. In 1949, Moe Abramson and Stanislaus F. Danko of the United States Army Signal Corps developed the Auto-Sembly process in which component leads were inserted into a copper foil interconnection pattern and dip soldered. With the development of board lamination and etching techniques, this concept evolved into the standard printed circuit board fabrication process in use today. Soldering could be done automatically by passing the board over a ripple, or wave, of molten solder in a wave-soldering machine. However, the wires and holes are wasteful since drilling holes is expensive and the protruding wires are merely cut off.


In recent years, the use of surface mount parts has gained popularity as the demand for smaller electronics packaging and greater functionality has grown.

Ohm

This article is about the SI (Omega) derived unit. For other meanings, see Ohm (disambiguation).

A multimeter can be used to measure resistance in ohms. It can also be used to measure capacitance, voltage, current, and other electrical characteristics.

Several resistors. Their resistance, in ohms, is marked using a color code.

The ohm (symbol: Ω) is the SI unit of electrical impedance or, in the direct current case, electrical resistance, named after Georg Simon Ohm.



Definition

The ohm is defined as a resistance between 2 points of a conductor when a constant potential difference of 1 volt, applied to these points, produces in the conductor a current of 1 ampere, the conductor not being the seat of any electromotive force.[1]

In many cases the resistance of a conductor in ohms is approximately constant within a certain range of voltages, temperatures, and other parameters; one speaks of linear resistors. In other cases resistance varies (e.g., thermistors).

Commonly used multiples and submultiples in electrical and electronic usage are the milliohm, ohm, kilohm, and megohm.[2]





Use of the Ω symbol in electronic documents

Care should be taken when preparing documents (including HTML documents) which make use of the symbol Ω. Some document editing software will attempt to use the symbol typeface to render the character. Where the font is not supported, a W is displayed instead. As this represents the SI unit of power, not resistance, this can lead to confusion.

Unicode encodes an ohm symbol distinct from Greek omega among Letterlike Symbols.

Volt

The volt (symbol: V) is the SI derived unit of electromotive force, commonly called "voltage".[1] It is also the unit for the related but slightly different quantity electric potential difference (also called "electrostatic potential difference"). It is named in honor of the Italian physicist Alessandro Volta (1745–1827), who invented the voltaic pile, possibly the first chemical battery.

Definition

The volt is defined as the value of the voltage across a conductor when a current of one ampere dissipates one watt of power in the conductor.[2] It can be written in terms of SI base units as: m2 • kg • s−3 • A−1. It is also equal to one joule of energy per coulomb of charge, J/C.

Josephson junction definition

Since 1990 the volt has been maintained internationally for practical measurement using the Josephson effect, where a conventional value is used for the Josephson constant, fixed by the 18th General Conference on Weights and Measures as:

K{J-90} = 2e/h = 0.4835979 GHz/µV.

This is typically used with an array of several thousand or tens of thousands of junctions, excited by microwave signals between 10 and 80 GHz (depending on the array design).[ The relationship KJ = 2e/h is apparently exact, with no correction terms required in a practical implementation.


Common voltages


• Nerve cell resting potential: around −75 mV[5]


• Single-cell, rechargeable NiMH or NiCd battery: 1.2 V


• Mercury battery: 1.355 V


• Single-cell, non-rechargeable alkaline battery (e.g., AAA, AA, C and D cells): 1.5 V


• LiFePO4 rechargeable battery: 3.3 V


• Lithium polymer rechargeable battery: 3.75 V (see Rechargeable battery#Table of rechargeable battery technologies)


• Transistor-transistor logic/CMOS (TTL) power supply: 5 V


• PP3 battery: 9 V


• Automobile electrical system: nominal 12 V, about 11.8 V discharged, 12.8 V charged, and 13.8–14.4 V while charging (vehicle running).


• Household mains electricity: 230 V RMS in Europe, Asia and Africa, 120 V RMS in North America, 100 V RMS in Japan (see List of countries with mains power plugs, voltages and frequencies)


• Commercial and Military Jet aircraft: 400 V AC, 28 V DC[citation needed]


• Trucks/lorries: 24 V DC


• Rapid transit third rail: 600–750 V (see List of current systems for electric rail traction)


• High speed train overhead power lines: 25 kV RMS at 50 Hz, but see the list of current systems for electric rail traction and 25 kV at 60 Hz for exceptions.


• High voltage electric power transmission lines: 110 kV RMS and up (1.15 MV RMS was the record as of 2005[citation needed])


• Lightning: Varies greatly, often around 100 MV.


Note: Where RMS (root mean square) is stated above, the peak voltage is times greater than the RMS voltage for a sinusoidal signal centered around zero voltage.

History of the volt

In 1800, as the result of a professional disagreement over the galvanic response advocated by Luigi Galvani, Alessandro Volta developed the so-called Voltaic pile, a forerunner of the battery, which produced a steady electric current. Volta had determined that the most effective pair of dissimilar metals to produce electricity was zinc and silver. In the 1880s, the International Electrical Congress, now the International Electrotechnical Commission (IEC), approved the volt as the unit for electromotive force. At that time, the volt was defined as the potential difference [i.e., what is nowadays called the "voltage (difference)"] across a conductor when a current of one ampere dissipates one watt of power.


The international volt was defined in 1893 as 1/1.434 of the emf of a Clark cell. This definition was abandoned in 1908 in favor of a definition based on the international ohm and international ampere until the entire set of "reproducible units" was abandoned in 1948.

Prior to the development of the Josephson junction voltage standard, the volt was maintained in national laboratories using specially constructed batteries called standard cells. The United States used a design called the Weston cell from 1905 to 1972.

This SI unit is named after Alessandro Volta. As with every SI unit whose name is derived from the proper name of a person, the first letter of its symbol is uppercase (V). When an SI unit is spelled out in English, it should always begin with a lowercase letter (volt), except where any word would be capitalized, such as at the beginning of a sentence or in capitalized material such as a title. Note that "degree Celsius" conforms to this rule because the "d" is lowercase.

—Based on The International System of Units,

Sony Alpha DSLR- A850 Full Frame Digital SLR Camera

Sony Alpha DSLR- A850 Full Frame Digital SLR Camera

• Full Frame Image Sensor (24 x 36mm)
• High Resolution (24.6 Megapixels)
• High Sensitivity (ISO 6400)
• Dual Noise Reduction Processing
• SteadyShot INSIDE Image Stabilization
• 3.0" Xtra Fine LCD
• 9-Point Auto Focusing
• 40-Segment Multi-Pattern Metering
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• 13 Creative Style Modes

9W Power Amplifier

The TDA1010 is a monolithic integrated class-B audio amplifier circuit in a 9-lead single in-line (SIL) plastic package. The device is primarily developed as a 6 W car radio amplifier for use with 4 Wand 2 Wload impedances. The wide supply voltage range and the flexibility of the IC make it an attractive proposition for record players and tape recorders with output powers up to 10 W.

50W Power Amplifier

Here is Power Amplifier 50W Circuit,Use IC STK1050. OCL Class AB Amp.

Voltage supply +35V , -35V 2-3A / Ch

bending movment

On the Design of Damaged Steel Columns


• Emeritus Professor Nick Trahair

• Kourosh Kayvani (Connell Wagner)

This project explores a number of situations where columns with out-of-tolerance crookedness or which have been damaged may still be designed, despite the implications of many codes that they must be replaced, and has suggested rules for their design. The case of a column whose crookedness is out-of-tolerance is first examined, and two design methods are suggested. In the first method, the column is treated in a similar way to that used for the basis of the BS5950 column design method by allowing for the excess crookednesses. In the second method, the column is designed as a straight beam-column with design moments equal to those resulting from the first-order analysis of an imperfect structure whose geometry includes the excess crookednesses.



Following this, the case is considered of a column damaged by unexpected bending which leaves an out-of-tolerance permanent set. It is concluded that the residual stresses caused by the damaging bending moments can be ignored, and the damaged column can be designed for its increased crookedness by using either of the methods proposed for columns with out-of-tolerance crookedness. The straightening of the damaged column was also considered. It was found that the residual stresses which follow relaxation after straightening can also be ignored and the column designed in the usual way.



Finally, the case is analysed of a force-fitted column which has excessive crookedness locked in during its connection to other members of a structure. It is found that the force-fitting deflection can be regarded as an initial crookedness, so that the column can be designed as an out-of-tolerance column.



Trahair, NS and Kayvani, K 'Capacities of Steel Columns with Excessive Crookedness', The Structural Engineer, 84 (4), 2006, pp 37 - 41, and School of Civil Engineering Research Report R 846.

dambulla history

Dambulla is situated exactly 160Km from Colombo. It is situated at the very end of north western province and the right beginning of the north central province. Dambulla is one of the places of historical importance in Sri Lanka.

Dambulla is a historical city. Tourists who come to Sri Lanka never fail to visit Dambulla. There main attractions are Dambulla historical temple and Sigiriya fortress. Sigiriya is situated about 10Km away from Dambulla, other attractive places are Kandalama tank, Namal uyana and Kaludiya Pokuna.
This city belongs to the dry zone.

The largest market of Sri Lanka is situated in Dambulla. It is called “The Economic Center”. The city becomes very busy during the evening until late in the night since it is the center of distribution of vegetable to the entire country. Almost all the vegetables grown in Sri Lanka can be seen in Dambulla.
You can see a lot of indigenous and migrant birds at Kandalama. Dambulla has a hot and humid climate throughout the year. Wild elephants too can be seen at habarana, a village situated few miles away from Dambulla. The ebony and the satin wood are the valuable trees grow in his area.There are an international level cricket stadium too in Dambulla. Nearly twenty hotels in and around Dambulla provides all the modern facility for tourist.

segiry history

"Lion's rock" is an ancient rock fortress and palace ruin situated in the central Matale district of Sri Lanka surrounded by the remains of an extensive network of gardens, reservoirs, and other structures. Sigiriya is world famous for its frescoes.

A popular tourist destination, Sigiriya is also renowned for its ancient paintings which are reminiscent of the Ajanta Caves ofI ndia. The Sigiriya was built during the reign of King Kassapa I (AD 477 – 495), and it is one of the seven World Heritage Sites of Sri Lanka.

Sigiriya may have been inhabited through prehistoric times. It was used as a rock-shelter mountain monastery from about the 5th century BC, with caves prepared and donated by devotees to the Buddhist Sangha.

The garden and palace were built by King Kasyapa. Following King Kasyapa's death, it was again a monastery complex up to about the 14th century, after which it was abandoned.The Sigiri inscriptions were deciphered by the archaeologist Senarath Paranavithana in his renowned two-volume work, published by Oxford, Sigiri Graffiti. He also wrote the popular book "Story of Sigiriya".

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