physics physics, branch of science traditionally defined as the study of matter, energy, and the relation between them; it was called natural philosophy until the late 19th cent. and is still known by this name at a few universities. Physics is in some senses the oldest and most basic pure science; its discoveries find applications throughout the natural sciences, since matter and energy are the basic constituents of the natural world. The other sciences are generally more limited in their scope and may be considered branches that have split off from physics to become sciences in their own right. Physics today may be divided loosely into classical physics and modern physics. Classical Physics Classical physics includes the traditional branches and topics that were recognized and fairly well developed before the beginning of the 20th cent.—mechanics, sound, light, heat, and electricity and magnetism. Mechanics is concerned with bodies acted on by forces and bodies in motion and may be divided into statics (study of the forces on a body or bodies at rest), kinematics (study of motion without regard to its causes), and dynamics (study of motion and the forces that affect it); mechanics may also be divided into solid mechanics and fluid mechanics, the latter including such branches as hydrostatics, hydrodynamics, aerodynamics, and pneumatics. Acoustics, the study of sound, is often considered a branch of mechanics because sound is due to the motions of the particles of air or other medium through which sound waves can travel and thus can be explained in terms of the laws of mechanics. Among the important modern branches of acoustics is ultrasonics, the study of sound waves of very high frequency, beyond the range of human hearing. Optics, the study of light, is concerned not only with visible light but also with infrared and ultraviolet radiation, which exhibit all of the phenomena of visible light except visibility, e.g., reflection, refraction, interference, diffraction, dispersion (see spectrum), and polarization of light. Heat is a form of energy, the internal energy possessed by the particles of which a substance is composed; thermodynamics deals with the relationships between heat and other forms of energy. Electricity and magnetism have been studied as a single branch of physics since the intimate connection between them was discovered in the early 19th cent.; an electric current gives rise to a magnetic field and a changing magnetic field induces an electric current. Electrostatics deals with electric charges at rest, electrodynamics with moving charges, and magnetostatics with magnetic poles at rest. Modern Physics Most of classical physics is concerned with matter and energy on the normal scale of observation; by contrast, much of modern physics is concerned with the behavior of matter and energy under extreme conditions or on the very large or very small scale. For example, atomic and nuclear physics studies matter on the smallest scale at which chemical elements can be identified. The physics of elementary particles is on an even smaller scale, being concerned with the most basic units of matter; this branch of physics is also known as high-energy physics because of the extremely high energies necessary to produce many types of particles in large particle accelerators. On this scale, ordinary, commonsense notions of space, time, matter, and energy are no longer valid. The two chief theories of modern physics present a different picture of the concepts of space, time, and matter from that presented by classical physics. The quantum theory is concerned with the discrete, rather than continuous, nature of many phenomena at the atomic and subatomic level, and with the complementary aspects of particles and waves in the description of such phenomena. The theory of relativity is concerned with the description of phenomena that take place in a frame of reference that is in motion with respect to an observer; the special theory of relativity is concerned with relative uniform motion in a straight line and the general theory of relativity with accelerated motion and its connection with gravitation. Both the quantum theory and the theory of relativity find applications in all areas of modern physics. Evolution of Physics Greek Contributions The earliest history of physics is interrelated with that of the other sciences. A number of contributions were made during the period of Greek civilization, dating from Thales and the early Ionian natural philosophers in the Greek colonies of Asia Minor (6th and 5th cent. B.C.). Democritus (c.460–370 B.C.) proposed an atomic theory of matter and extended it to other phenomena as well, but the dominant theories of matter held that it was formed of a few basic elements, usually earth, air, fire, and water. In the school founded by Pythagoras of Samos the principal concept was that of number; it was applied to all aspects of the universe, from planetary orbits to the lengths of strings used to sound musical notes. The most important philosophy of the Greek period was produced by two men at Athens, Plato (427–347 B.C.) and his student Aristotle (384–322 B.C.); Aristotle in particular had a critical influence on the development of science in general and physics in particular. The Greek approach to physics was largely geometrical and reached its peak with Archimedes (287–212 B.C.), who studied a wide range of problems and anticipated the methods of the calculus. Another important scientist of the early Hellenistic period, centered in Alexandria, Egypt, was the astronomer Aristarchus (c.310–220 B.C.), who proposed a heliocentric, or sun-centered, system of the universe. However, just as the earlier atomic theory had not become generally accepted, so too the astronomical system that eventually prevailed was the geocentric system proposed by Hipparchus (190–120 B.C.) and developed in detail by Ptolemy (A.D. 85–A.D. 165). Preservation of Learning With the passing of the Greek civilization and the Roman civilization that followed it, Greek learning passed into the hands of the Muslim world that spread its influence from the E Mediterranean eastward into Asia, where it picked up contributions from the Chinese (papermaking, gunpowder) and the Hindus (the place-value decimal number system with a zero), and westward as far as Spain, where Islamic culture flourished in Córdoba, Toledo, and other cities. Little specific advance was made in physics during this period, but the preservation and study of Greek science by the Muslim world made possible the revival of learning in the West beginning in the 12th and 13th cent. The Scientific Revolution The first areas of physics to receive close attention were mechanics and the study of planetary motions. Modern mechanics dates from the work of Galileo and Simon Stevin in the late 16th and early 17th cent. The great breakthrough in astronomy was made by Nicolaus Copernicus, who proposed (1543) the heliocentric model of the solar system that was later modified by Johannes Kepler (using observations by Tycho Brahe) into the description of planetary motions that is still accepted today. Galileo gave his support to this new system and applied his discoveries in mechanics to its explanation. The full explanation of both celestial and terrestrial motions was not given until 1687, when Isaac Newton published his Principia [Mathematical Principles of Natural Philosophy]. This work, the most important document of the Scientific Revolution of the 16th and 17th cent., contained Newton's famous three laws of motion and showed how the principle of universal gravitation could be used to explain the behavior not only of falling bodies on the earth but also planets and other celestial bodies in the heavens. To arrive at his results, Newton invented one form of an entirely new branch of mathematics, the calculus (also invented independently by G. W. Leibniz), which was to become an essential tool in much of the later development in most branches of physics. Other branches of physics also received attention during this period. William Gilbert, court physician to Queen Elizabeth I, pub

Physcisearl.blogspot.com

physics physics, branch of science traditionally defined as the study of matter, energy, and the relation between them; it was called natural philosophy until the late 19th cent. and is still known by this name at a few universities. Physics is in some senses the oldest and most basic pure science; its discoveries find applications throughout the natural sciences, since matter and energy are the basic constituents of the natural world. The other sciences are generally more limited in their scope and may be considered branches that have split off from physics to become sciences in their own right. Physics today may be divided loosely into classical physics and modern physics. Classical Physics Classical physics includes the traditional branches and topics that were recognized and fairly well developed before the beginning of the 20th cent.—mechanics, sound, light, heat, and electricity and magnetism. Mechanics is concerned with bodies acted on by forces and bodies in motion and may be divided into statics (study of the forces on a body or bodies at rest), kinematics (study of motion without regard to its causes), and dynamics (study of motion and the forces that affect it); mechanics may also be divided into solid mechanics and fluid mechanics, the latter including such branches as hydrostatics, hydrodynamics, aerodynamics, and pneumatics. Acoustics, the study of sound, is often considered a branch of mechanics because sound is due to the motions of the particles of air or other medium through which sound waves can travel and thus can be explained in terms of the laws of mechanics. Among the important modern branches of acoustics is ultrasonics, the study of sound waves of very high frequency, beyond the range of human hearing. Optics, the study of light, is concerned not only with visible light but also with infrared and ultraviolet radiation, which exhibit all of the phenomena of visible light except visibility, e.g., reflection, refraction, interference, diffraction, dispersion (see spectrum), and polarization of light. Heat is a form of energy, the internal energy possessed by the particles of which a substance is composed; thermodynamics deals with the relationships between heat and other forms of energy. Electricity and magnetism have been studied as a single branch of physics since the intimate connection between them was discovered in the early 19th cent.; an electric current gives rise to a magnetic field and a changing magnetic field induces an electric current. Electrostatics deals with electric charges at rest, electrodynamics with moving charges, and magnetostatics with magnetic poles at rest. Modern Physics Most of classical physics is concerned with matter and energy on the normal scale of observation; by contrast, much of modern physics is concerned with the behavior of matter and energy under extreme conditions or on the very large or very small scale. For example, atomic and nuclear physics studies matter on the smallest scale at which chemical elements can be identified. The physics of elementary particles is on an even smaller scale, being concerned with the most basic units of matter; this branch of physics is also known as high-energy physics because of the extremely high energies necessary to produce many types of particles in large particle accelerators. On this scale, ordinary, commonsense notions of space, time, matter, and energy are no longer valid. The two chief theories of modern physics present a different picture of the concepts of space, time, and matter from that presented by classical physics. The quantum theory is concerned with the discrete, rather than continuous, nature of many phenomena at the atomic and subatomic level, and with the complementary aspects of particles and waves in the description of such phenomena. The theory of relativity is concerned with the description of phenomena that take place in a frame of reference that is in motion with respect to an observer; the special theory of relativity is concerned with relative uniform motion in a straight line and the general theory of relativity with accelerated motion and its connection with gravitation. Both the quantum theory and the theory of relativity find applications in all areas of modern physics. Evolution of Physics Greek Contributions The earliest history of physics is interrelated with that of the other sciences. A number of contributions were made during the period of Greek civilization, dating from Thales and the early Ionian natural philosophers in the Greek colonies of Asia Minor (6th and 5th cent. B.C.). Democritus (c.460–370 B.C.) proposed an atomic theory of matter and extended it to other phenomena as well, but the dominant theories of matter held that it was formed of a few basic elements, usually earth, air, fire, and water. In the school founded by Pythagoras of Samos the principal concept was that of number; it was applied to all aspects of the universe, from planetary orbits to the lengths of strings used to sound musical notes. The most important philosophy of the Greek period was produced by two men at Athens, Plato (427–347 B.C.) and his student Aristotle (384–322 B.C.); Aristotle in particular had a critical influence on the development of science in general and physics in particular. The Greek approach to physics was largely geometrical and reached its peak with Archimedes (287–212 B.C.), who studied a wide range of problems and anticipated the methods of the calculus. Another important scientist of the early Hellenistic period, centered in Alexandria, Egypt, was the astronomer Aristarchus (c.310–220 B.C.), who proposed a heliocentric, or sun-centered, system of the universe. However, just as the earlier atomic theory had not become generally accepted, so too the astronomical system that eventually prevailed was the geocentric system proposed by Hipparchus (190–120 B.C.) and developed in detail by Ptolemy (A.D. 85–A.D. 165). Preservation of Learning With the passing of the Greek civilization and the Roman civilization that followed it, Greek learning passed into the hands of the Muslim world that spread its influence from the E Mediterranean eastward into Asia, where it picked up contributions from the Chinese (papermaking, gunpowder) and the Hindus (the place-value decimal number system with a zero), and westward as far as Spain, where Islamic culture flourished in Córdoba, Toledo, and other cities. Little specific advance was made in physics during this period, but the preservation and study of Greek science by the Muslim world made possible the revival of learning in the West beginning in the 12th and 13th cent. The Scientific Revolution The first areas of physics to receive close attention were mechanics and the study of planetary motions. Modern mechanics dates from the work of Galileo and Simon Stevin in the late 16th and early 17th cent. The great breakthrough in astronomy was made by Nicolaus Copernicus, who proposed (1543) the heliocentric model of the solar system that was later modified by Johannes Kepler (using observations by Tycho Brahe) into the description of planetary motions that is still accepted today. Galileo gave his support to this new system and applied his discoveries in mechanics to its explanation. The full explanation of both celestial and terrestrial motions was not given until 1687, when Isaac Newton published his Principia [Mathematical Principles of Natural Philosophy]. This work, the most important document of the Scientific Revolution of the 16th and 17th cent., contained Newton's famous three laws of motion and showed how the principle of universal gravitation could be used to explain the behavior not only of falling bodies on the earth but also planets and other celestial bodies in the heavens. To arrive at his results, Newton invented one form of an entirely new branch of mathematics, the calculus (also invented independently by G. W. Leibniz), which was to become an essential tool in much of the later development in most branches of physics. Other branches of physics also received attention during this period. William Gilbert, court physician to Queen Elizabeth I, pub

HOW NANOTECHNOLOGY WORKS

There's an unprecedented multidisciplinary convergence of scientists dedicated to the study of a world so small, we can't see it -- even with a light microscope. That world is the field of nanotechnology, the realm of atoms and nanostructures. Nanotechnology i­s so new, no one is really sure what will come of it. Even so, predictions range from the ability to reproduce things like diamonds and food to the world being devoured by self-replicating nanorobots.

In order to understand the unusual world of nanotechnology, we need to get an idea of the units of measure involved. A centimeter is one-hundredth of a meter, a millimeter is one-thousandth of a meter, and a micrometer is one-millionth of a meter, but all of these are still huge compared to the nanoscale. A nanometer (nm) is one-billionth of a meter, smaller than the wavelength of visible light and a hundred-thousandth the width of a human hair [source: Berkeley Lab].

As small as a nanometer is, it's still large compared to the atomic scale. An atom has a diameter of about 0.1 nm. An atom's nucleus is much smaller -- about 0.00001 nm. Atoms are the building blocks for all matter in our universe. You and everything around you are made of atoms. Nature has perfected the science of manufacturing matter molecularly. For instance, our bodies are assembled in a specific manner from millions of living cells. Cells are nature's nanomachines. At the atomic scale, elements are at their most basic level. On the nanoscale, we can potentially put these atoms together to make almost anything.

In a lecture called "Small Wonders:The World of Nanoscience," Nobel Prize winner Dr. Horst Störmer said that the nanoscale is more interesting than the atomic scale because the nanoscale is the first point where we can assemble something -- it's not until we start putting atoms together that we can make anything useful.

In this article, we'll learn about what nanotechnology means today and what the future of nanotechnology may hold. We'll also look at the potential risks that come with working at the nanoscale.

The World of Nanotechnology

Experts sometimes disagree about what constitutes the nanoscale, but in general, you can think of nanotechnology dealing with anything measuring between 1 and 100 nm. Larger than that is the microscale, and smaller than that is the atomic scale.

Nanotechnology is rapidly becoming an interdisciplinary field. Biologists, chemists, physicists and engineers are all involved in the study of substances at the nanoscale. Dr. Störmer hopes that the different disciplines develop a common language and communicate with one another [source: Störmer]. Only then, he says, can we effectively teach nanoscience since you can't understand the world of nanotechnology without a solid background in multiple sciences.

One of the exciting and challenging aspects of the nanoscale is the role that quantum mechanics plays in it. The rules of quantum mechanics are very different from classical physics, ­which means that the behavior of substances at the nanoscale can sometimes contradict common sense by behaving erratically. You can't walk up to a wall and immediately teleport to the other side of it, but at the nanoscale an electron can -- it's called electron tunneling. Substances that are insulators, meaning they can't carry an electric charge, in bulk form might become semiconductors when reduced to the nanoscale. Melting points can change due to an increase in surface area. Much of nanoscience requires that you forget what you know and start learning all over again.

So what does this all mean? Right now, it means that scientists are experimenting with substances at the nanoscale to learn about their properties and how we might be able to take advantage of them in various applications. Engineers are trying to use nano-size wires to create smaller, more powerful microprocessors. Doctors are searching for ways to use nanoparticles in medical applications. Still, we've got a long way to go before nanotechnology dominates the technology and medical markets.

Nanowires and Carbon Nanotubes

Currently, scientists find two nano-size structures of particular interest: nanowires and carbon nanotubes. Nanowires are wires with a very small diameter, sometimes as small as 1 nanometer. Scientists hope to use them to build tiny transistors for computer chips and other electronic devices. In the last couple of years, carbon nanotubes have overshadowed nanowires. We're still learning about these structures, but what we've learned so far is very exciting.

A carbon nanotube is a nano-size cylinder of carbon atoms. Imagine a sheet of carbon atoms, which would look like a sheet of hexagons. If you roll that sheet into a tube, you'd have a carbon nanotube. Carbon nanotube properties depend on how you roll the sheet. In other words, even though all carbon nanotubes are made of carbon, they can be very different from one another based on how you align the individual atoms.

With the right arrangement of atoms, you can create a carbon nanotube that's hundreds of times stronger than steel, but six times lighter [source: The Ecologist]. Engineers plan to make building material out of carbon nanotubes, particularly for things like cars and airplanes. Lighter vehicles would mean better fuel efficiency, and the added strength translates to increased passenger safety.

Carbon nanotubes can also be effective semiconductors with the right arrangement of atoms. Scientists are still working on finding ways to make carbon nanotubes a realistic option for transistors in microprocessors and other electronics.

Products with Nanotechnology

You might be surprised to find out how many products on the market are already benefiting from nanotechnology.

Bridgestone engineers developed this Quick Response Liquid Powder Display, a flexible digital screen, using nanotechnology.

Sunscreen - Many sunscreens contain nanoparticles of zinc oxide or titanium oxide. Older sunscreen formulas use larger particles, which is what gives most sunscreens their whitish color. Smaller particles are less visible, meaning that when you rub the sunscreen into your skin, it doesn't give you a whitish tinge.
Self-cleaning glass - A company called Pilkington offers a product they call Activ Glass, which uses nanoparticles to make the glass photocatalytic and hydrophilic. The photocatalytic effect means that when UV radiation from light hits the glass, nanoparticles become energized and begin to break down and loosen organic molecules on the glass (in other words, dirt). Hydrophilic means that when water makes contact with the glass, it spreads across the glass evenly, which helps wash the glass clean.
Clothing - Scientists are using nanoparticles to enhance your clothing. By coating fabrics with a thin layer of zinc oxide nanoparticles, manufacturers can create clothes that give better protection from UV radiation. Some clothes have nanoparticles in the form of little hairs or whiskers that help repel water and other materials, making the clothing stain-resistant.
Scratch-resistant coatings - Engineers discovered that adding aluminum silicate nanoparticles to scratch-resistant polymer coatings made the coatings more effective, increasing resistance to chipping and scratching. Scratch-resistant coatings are common on everything from cars to eyeglass lenses.
Antimicrobial bandages - Scientist Robert Burrell created a process to manufacture antibacterial bandages using nanoparticles of silver. Silver ions block microbes' cellular respiration [source: Burnsurgery.org]. In other words, silver smothers harmful cells, killing them.

New products incorporating nanotechnology are coming out every day. Wrinkle-resistant fabrics, deep-penetrating cosmetics, liquid crystal displays (LCD) and other conveniences using nanotechnology are on the market. Before long, we'll see dozens of other products that take advantage of nanotechnology ranging from Intel microprocessors to bio-nanobatteries, capacitors only a few nanometers thick. While this is exciting, it's only the tip of the iceberg as far as how nanotechnology may impact us in the future.

The Future of Nanotechnology

In the world of "Star Trek," machines called replicators can produce practically any physical object, from weapons to a steaming cup of Earl Grey tea. Long considered to be exclusively the product of science fiction, today some people believe replicators are a very real possibility. They call it molecular manufacturing, and if it ever does become a reality, it could drastically change the world.

Atoms and molecules stick together because they have complementary shapes that lock together, or charges that attract. Just like with magnets, a positively charged atom will stick to a negatively charged atom. As millions of these atoms are pieced together by nanomachines, a specific product will begin to take shape. The goal of molecular manufacturing is to manipulate atoms individually and place them in a pattern to produce a desired structure.

The first step would be to develop nanoscopic machines, called assemblers, that scientists can program to manipulate atoms and molecules at will. Rice University Professor Richard Smalley points out that it would take a single nanoscopic machine millions of years to assemble a meaningful amount of material. In order for molecular manufacturing to be practical, you would need trillions of assemblers working together simultaneously. Eric Drexler believes that assemblers could first replicate themselves, building other assemblers. Each generation would build another, resulting in exponential growth until there are enough assemblers to produce objects.

Trillions of assemblers and replicators could fill an area smaller than a cubic millimeter, and could still be too small for us to see with the naked eye. Assemblers and replicators could work together to automatically construct products, and could eventually replace all traditional labor methods. This could vastly decrease manufacturing costs, thereby making consumer goods plentiful, cheaper and stronger. Eventually, we could be able to replicate anything, including diamonds, water and food. Famine could be eradicated by machines that fabricate foods to feed the hungry.

Nanotechnology may have its biggest impact on the medical industry. Patients will drink fluids containing nanorobots programmed to attack and reconstruct the molecular structure of cancer cells and viruses. There's even speculation that nanorobots could slow or reverse the aging process, and life expectancy could increase significantly. Nanorobots could also be programmed to perform delicate surgeries -- such nanosurgeons could work at a level a thousand times more precise than the sharpest scalpel [source: International Journal of Surgery]. By working on such a small scale, a nanorobot could operate without leaving the scars that conventional surgery does. Additionally, nanorobots could change your physical appearance. They could be programmed to perform cosmetic surgery, rearranging your atoms to change your ears, nose, eye color or any other physical feature you wish to alter.

Nanotechnology has the potential to have a positive effect on the environment. For instance, scientists could program airborne nanorobots to rebuild the thinning ozone layer. Nanorobots could remove contaminants from water sources and clean up oil spills. Manufacturing materials using the bottom-up method of nanotechnology also creates less pollution than conventional manufacturing processes. Our dependence on non-renewable resources would diminish with nanotechnology. Cutting down trees, mining coal or drilling for oil may no longer be necessary -- nanomachines could produce those resources.

Many nanotechnology experts feel that these applications are well outside the realm of possibility, at least for the foreseeable future. They caution that the more exotic applications are only theoretical. Some worry that nanotechnology will end up like virtual reality -- in other words, the hype surrounding nanotechnology will continue to build until the limitations of the field become public knowledge, and then interest (and funding) will quickly dissipate.

Nanotechnology Challenges, Risks and Ethics

The most immediate challenge in nanotechnology is that we need to learn more about materials and their properties at the nanoscale. Universities and corporations across the world are rigorously studying how atoms fit together to form larger structures. We're still learning about how quantum mechanics impact substances at the nanoscale.

Because elements at the nanoscale behave differently than they do in their bulk form, there's a concern that some nanoparticles could be toxic. Some doctors worry that the nanoparticles are so small, that they could easily cross the blood-brain barrier, a membrane that protects the brain from harmful chemicals in the bloodstream. If we plan on using nanoparticles to coat everything from our clothing to our highways, we need to be sure that they won't poison us.

Closely related to the knowledge barrier is the technical barrier. In order for the incredible predictions regarding nanotechnology to come true, we have to find ways to mass produce nano-size products like transistors and nanowires. While we can use nanoparticles to build things like tennis rackets and make wrinkle-free fabrics, we can't make really complex microprocessor chips with nanowires yet.

There are some hefty social concerns about nanotechnology too. Nanotechnology may also allow us to create more powerful weapons, both lethal and non-lethal. Some organizations are concerned that we'll only get around to examining the ethical implications of nanotechnology in weaponry after these devices are built. They urge scientists and politicians to examine carefully all the possibilities of nanotechnology before designing increasingly powerful weapons.

If nanotechnology in medicine makes it possible for us to enhance ourselves physically, is that ethical? In theory, medical nanotechnology could make us smarter, stronger and give us other abilities ranging from rapid healing to night vision. Should we pursue such goals? Could we continue to call ourselves human, or would we become transhuman -- the next step on man's evolutionary path? Since almost every technology starts off as very expensive, would this mean we'd create two races of people -- a wealthy race of modified humans and a poorer population of unaltered people? We don't have answers to these questions, but several organizations are urging nanoscientists to consider these implications now, before it becomes too late.

Not all questions involve altering the human body -- some deal with the world of finance and economics. If molecular manufacturing becomes a reality, how will that impact the world's economy? Assuming we can build anything we need with the click of a button, what happens to all the manufacturing jobs? If you can create anything using a replicator, what happens to currency? Would we move to a completely electronic economy? Would we even need money?

Whether we'll actually need to answer all of these questions is a matter of debate. Many experts think that concerns like grey goo and transhumans are at best premature, and probably unnecessary. Even so, nanotechnology will definitely continue to impact us as we learn more about the enormous potential of the nanoscale.

The Difference between an Inverter and UPS

The basic difference in layman's terms is:

While both provide backup power during mains outage, with the UPS the switch is instantaneous whereas with the Inverter there is a gap of a second or two. This gap is OK for household gadgets such as lights, fans, fridge, etc. but not OK for computers.

In technical terms:

UPS: The mains power comes to the UPS. The AC is converted to DC and this DC is constantly charging the battery. The output of the battery is fed to the Sine wave inverter and it converts DC to AC and this feeds the equipment. Since power out is always drawn from the battery, there is no time lag when mains swicthes off; it justs stops the battery from being charged and the UPS continues to supply power till the battery runs out.

Inverter: The mains power comes to the Inverter. This is directly sent to the output but the AC is also converted to DC and this DC is constantly charging the battery. A sensor and relay mechanism checks whether the mains is ON or OFF. When the main switches OFF, the relay actuator triggers to switch from mains to inverter. Rest is same like the UPS. Because of this sensor and relay, there is a gap between triggering.

UPS involves more costly circuitary and is therefor more expensive to make and sell.

THE DESCRIPTION OF HOW A POWER GRID WORKS

Electrical power is a little bit like the air you breathe: You don't really think about it until it is missing. Power is just "there," meeting your every need, constantly.

It's only during a power failure, when you walk into a dark room and instinctively hit the useless light switch, that you realize how important power is in your daily life.

You use it for heating, cooling, cooking, refrigeration, light, sound, computation, entertainment... Without power, life can get somewhat cumbersome.

Power travels from the power plant to your house through an amazing system called the power distribution grid.

The grid is quite public -- if you live in a suburban or rural area, chances are it is right out in the open for all to see. It is so public, in fact, that you probably don't even notice it anymore. Your brain likely ignores all of the power lines because it has seen them so often.

The Power Plant


Electrical power starts at the power plant. In almost all cases, the power plant consists of a spinning electrical generator. Something has to spin that generator -- it might be a water wheel in a hydroelectric dam, a large diesel engine or a gas turbine. But in most cases, the thing spinning the generator is a steam turbine. The steam might be created by burning coal, oil or natural gas. Or the steam may come from a nuclear reactor like this one at the Shearon Harris nuclear power plant near Raleigh, North Carolina.

No matter what it is that spins the generator, commercial electrical generators of any size generate what is called 3-phase AC power. To understand 3-phase AC power, it is helpful to understand single-phase power first.

The Power Plant: Alternating Current

­Single-phase power is what you have in your house. You generally talk about household electrical service as single-phase, 120-volt AC service. If you use an oscilloscope and look at the power found at a normal wall-plate outlet in your house, what you will find is that the power at the wall plate looks like a sine wave, and that wave oscillates between -170 volts and 170 volts (the peaks are indeed at 170 volts; it is the effective (rms) voltage that is 120 volts). The rate of oscillation for the sine wave is 60 cycles per second. Oscillating power like this is generally referred to as AC, or alternating current. The alternative to AC is DC, or direct current. Batteries produce DC: A steady stream of electrons flows in one direction only, from the negative to the positive terminal of the battery.

AC has at least three advantages over DC in a power distribution grid:

1.Large electrical generators happen to generate AC naturally, so conversion to DC would involve an extra step.
2.Transformers must have alternating current to operate, and we will see that the power distribution grid depends on transformers.
3.It is easy to convert AC to DC but expensive to convert DC to AC, so if you were going to pick one or the other AC would be the better choice.
The power plant, therefore, produces AC.

The Power Plant: Three-phase Power


The power plant produces three different phases of AC power simultaneously, and the three phases are offset 120 degrees from each other. There are four wires coming out of every power plant: the three phases plus a neutral or ground common to all three. If you were to look at the three phases on a graph, they would look like this relative to ground:

There is nothing magical about three-phase power. It is simply three single phases synchronized and offset by 120 degrees.

Why three phases? Why not one or two or four? In 1-phase and 2-phase power, there are 120 moments per second when a sine wave is crossing zero volts. In 3-phase power, at any given moment one of the three phases is nearing a peak. High-power 3-phase motors (used in industrial applications) and things like 3-phase welding equipment therefore have even power output. Four phases would not significantly improve things but would add a fourth wire, so 3-phase is the natural settling point.

And what about this "ground," as mentioned above? The power company essentially uses the earth as one of the wires in the power system. The earth is a pretty good conductor and it is huge, so it makes a good return path for electrons. (Car manufacturers do something similar; they use the metal body of the car as one of the wires in the car's electrical system and attach the negative pole of the battery to the car's body.) "Ground" in the power distribution grid is literally "the ground" that's all around you when you are walking outside. It is the dirt, rocks, groundwater, etc., of the earth.

Transmission Substation


The three-phase power leaves the generator and enters a transmission substation at the power plant. This substation uses large transformers to convert the generator's voltage (which is at the thousands of volts level) up to extremely high voltages for long-distance transmission on the transmission grid.

You can see at the back several three-wire towers leaving the substation. Typical voltages for long distance transmission are in the range of 155,000 to 765,000 volts in order to reduce line losses. A typical maximum transmission distance is about 300 miles (483 km). High-voltage transmission lines are quite obvious when you see them. They are normally made of huge steel towers like this:

All power towers like this have three wires for the three phases. Many towers, like the ones shown above, have extra wires running along the tops of the towers. These are ground wires and are there primarily in an attempt to attract lightning.


The Distribution Grid



For power to be useful in a home or business, it comes off the transmission grid and is stepped-down to the distribution grid. This may happen in several phases. The place where the conversion from "transmission" to "distribution" occurs is in a power substation. A power substation typically does two or three things:

It has transformers that step transmission voltages (in the tens or hundreds of thousands of volts range) down to distribution voltages (typically less than 10,000 volts).
It has a "bus" that can split the distribution power off in multiple directions.
It often has circuit breakers and switches so that the substation can be disconnected from the transmission grid or separate distribution lines can be disconnected from the substation when necessary.

The box in the foreground is a large transformer. To its left (and out of the frame but shown in the next shot) are the incoming power from the transmission grid and a set of switches for the incoming power. Toward the right is a distribution bus plus three voltage regulators.


The transmission lines entering the substation and passing through the switch tower


The switch tower and the main transformer

Distribution Bus


The power goes from the transformer to the distribution bus:

In this case, the bus distributes power to two separate sets of distribution lines at two different voltages. The smaller transformers attached to the bus are stepping the power down to standard line voltage (usually 7,200 volts) for one set of lines, while power leaves in the other direction at the higher voltage of the main transformer. The power leaves this substation in two sets of three wires, each headed down the road in a different direction:


The wires between these two poles are "guy wires" for support. They carry no current.

The next time you are driving down the road, you can look at the power lines in a completely different light. In the typical scene pictured on the right, the three wires at the top of the poles are the three wires for the 3-phase power. The fourth wire lower on the poles is the ground wire. In some cases there will be additional wires, typically phone or cable TV lines riding on the same poles.

As mentioned above, this particular substation produces two different voltages. The wires at the higher voltage need to be stepped down again, which will often happen at another substation or in small transformers somewhere down the line. For example, you will often see a large green box (perhaps 6 feet/1.8 meters on a side) near the entrance to a subdivision. It is performing the step-down function for the subdivision.


Regulator Bank


You will also find regulator banks located along the line, either underground or in the air. They regulate the voltage on the line to prevent undervoltage and overvoltage conditions.

Up toward the top are three switches that allow this regulator bank to be disconnected for maintenance when necessary:

At this point, we have typical line voltage at something like 7,200 volts running through the neighborhood on three wires (with a fourth ground wire lower on the pole):




Taps

A house needs only one of the three phases, so typically you will see three wires running down a main road, and taps for one or two of the phases running off on side streets. Pictured below is a 3-phase to 2-phase tap, with the two phases running off to the right:


Here is a 2-phase to 1-phase tap, with the single phase running out to the right:

At the House


And finally we are down to the wire that brings power to your house! Past a typical house runs a set of poles with one phase of power (at 7,200 volts) and a ground wire (although sometimes there will be two or three phases on the pole, depending on where the house is located in the distribution grid). At each house, there is a transformer drum attached to the pole, like this:

In many suburban neighborhoods, the distribution lines are underground and there are green transformer boxes at every house or two.

Here is some detail on what is going on at the pole:

The transformer's job is to reduce the 7,200 volts down to the 240 volts that makes up normal household electrical service. Let's look at this pole one more time, from the bottom, to see what is going on:




There are two things to notice in this picture:

There is a bare wire running down the pole. This is a grounding wire. Every utility pole on the planet has one. If you ever watch the power company install a new pole, you will see that the end of that bare wire is stapled in a coil to the base of the pole and therefore is in direct contact with the earth, running 6 to 10 feet (1.8 to 3 m) underground. It is a good, solid ground connection. If you examine a pole carefully, you will see that the ground wire running between poles (and often the guy wires) are attached to this direct connection to ground.
There are two wires running out of the transformer and three wires running to the house. The two from the transformer are insulated, and the third one is bare. The bare wire is the ground wire. The two insulated wires each carry 120 volts, but they are 180 degrees out of phase so the difference between them is 240 volts. This arrangement allows a homeowner to use both 120-volt and 240-volt appliances. The transformer is wired in this sort of configuration:

The 240 volts enters your house through a typical watt-hour meter like this one:

The meter lets the power company charge you for putting up all of these wires.


Safety Devices: Fuses


Fuses and circuit breakers are safety devices. Let's say that you did not have fuses or circuit breakers in your house and something "went wrong." What could possibly go wrong? Here are some examples:

A fan motor burns out a bearing, seizes, overheats and melts, causing a direct connection between power and ground.
A wire comes loose in a lamp and directly connects power to ground.
A mouse chews through the insulation in a wire and directly connects power to ground.
Someone accidentally vacuums up a lamp wire with the vacuum cleaner, cutting it in the process and directly connecting power to ground.
A person is hanging a picture in the living room and the nail used for said picture happens to puncture a power line in the wall, directly connecting power to ground.

When a 120-volt power line connects directly to ground, its goal in life is to pump as much electricity as possible through the connection. Either the device or the wire in the wall will burst into flames in such a situation. (The wire in the wall will get hot like the element in an electric oven gets hot, which is to say very hot!). A fuse is a simple device designed to overheat and burn out extremely rapidly in such a situation. In a fuse, a thin piece of foil or wire quickly vaporizes when an overload of current runs through it. This kills the power to the wire immediately, protecting it from overheating. Fuses must be replaced each time they burn out. A circuit breaker uses the heat from an overload to trip a switch, and circuit breakers are therefore resettable.

The power then enters the home through a typical circuit breaker panel like the one above.

Safety Devices: Circuit Breakers



Inside the circuit breaker panel you can see the two primary wires from the transformer entering the main circuit breaker at the top. The main breaker lets you cut power to the entire panel when necessary. Within this overall setup, all of the wires for the different outlets and lights in the house each have a separate circuit breaker or fuse:

If the circuit breaker is on, then power flows through the wire in the wall and makes its way eventually to its final destination, the outlet.

What an unbelievable story! It took all of that equipment to get power from the power plant to the light in your bedroom.

The next time you drive down the road and look at the power lines, or the next time you flip on a light, you'll hopefully have a much better understanding of what is going on. The power distribution grid is truly an incredible system.

Relation between Metaphysics and Physics

Physics is what has been defined, disproved and restated through ages of human research of all things around us, the keyword being around. People concur or debate over everything under, inside and far away from the Sun. They will deduce theorems and when found logical, term them as axioms. Then every once in a while, there comes along a thought or a phenomenon previously unaccounted for. It tinkers with the shackles with which we bind all happenings we know and understand. A classic example would be the statement on the earth being flat, later being evidently disproved and concluded with the new statement that the earth is indeed, round. There are so many similar comments and theories that have been cemented as fact, waiting for a 'spirited' sprite to set release them, only to have a new one to be found out and bound down.

The Relationship Between Physics and Metaphysics

Understanding Metaphysics
When put in paradigm, physics is the understanding of what we see, while metaphysics is the attempt to understand what we don't. Physics tells you the 'How' of all that you see around you. Metaphysics deals with the 'Why' of all things, around you and within you. Metaphysics aims to provide the definitive link between the apparent and the spiritual, without making concepts overly religious. Physics will define to the fullest, what can be observed and changed; anything beyond the observable, doesn't exist. The answer to the exactness of metaphysics is not describable, but can be understood from the classic question: "If a tree falls deep within a forest with no one around, does it still make a sound?". Whenever something happens within our surrounding, we may notice it with our senses. But when something happens outside this circle of knowledge, do we, or should we, believe that it has indeed happened? Now, if this occurrence from the unknown somehow affects the state of something within our circle of knowledge, how can we explain the chain of events? It is this that metaphysics wants to solve. So, while physics rules the plane of all known, physically realized phenomenon, metaphysics and all its branches sew together the universe of obscure and the phenomenon unexplained by physics. Physicist Stephen Hawking, who yearns to be in the know, said, "My goal is simple. It is a complete understanding of the universe, why it is as it is and why it exists at all". A point to be noted here is that metaphysics, or even ontology (the study of 'being') is not to be related or confused with the deviant sciences like occultism (the study of 'Forbidden knowledge') or esotericism (the study of alternative or secretive knowledge).

The Difference Between Physics and Metaphysics

* So what would be the primary point of distinction between the two? The answer has already been mentioned above, it is the difference between asking 'How' and 'Why'. Physics will always relate itself strictly to the functioning of a concept or a phenomenon, no matter its magnitude. Metaphysics will wrap itself around the reason of a concepts existence. It will keep asking, "What is the need of its creation?"; "What is its purpose?"; and "How will the matter affect other matter in the spiritual sense?". Or simply, thinking about the concept of thought itself. Metaphysics can also be called the study of the relationship between mind and matter.
* This point might be thought as ironic: religion. Ironic, because both physics and metaphysics refrain from going too close and actually fathom the deep end of religion. Religious discourses point to the existence of a Greater entity - God, and the purpose and reason of the existence of life - Creationism. Physics will refuse to acknowledge (or simply be indifferent towards) theology (the rational study of religion) altogether, concentrating on simply the nature and existence of all things. Physics may even disbar religion from its inner sanctums. Metaphysics will accept certain words from religion, in an attempt to explain what physics cannot. But even metaphysics will not accept the totality of God or the deviance from the theory of evolution.
* The set of rules that govern each side are a far cry from each other. While physics depends on reductionist laws and formulas, metaphysics is bound (or rather unbound) by its own rules; like the law of control (where the level of self-esteem of a person is directly proportional to the person's level of control over something), or the law of accident (where self-esteem depends on whether we are the victim of an occurrence uncontrolled by us).
* Physics will never jump outside a defined boundary of reason in search of a solution. Instead, it will make do with the things at hand and make the most of them, deriving a result agreeable by all within the boundary. But it's not that physics, by itself cannot expand its own boundaries. You can see breakthroughs that redefine classical physics everywhere. And then you'll also have metaphysics that always tends to push its own boundaries in search of truth, consequently establishing a new line of sight beyond what was initially imagined. This, in turn, creates even more questions about the new boundary, thereby requiring new answers. The cycle may never end and will probably encompass all aspects of knowledge, from the logical to the subconscious unknown, to the very ends of the universe itself.
* The definitive nature of physics that we know today rarely allows much miscalculations, making some theorems absolute (until of course, we know better). Metaphysics may always fall into a state of constant revision, until a final answer is attained or a new question poses itself. Metaphysics will always be an ever changing field due to its nature.

Points of Convergence
Despite the differences, there are some angles from which physics and metaphysics do seem alike. Physics may be hard-and-fast, but it will still be growing and changing. There can only be so long till when the laws of Newtonian physics will suffice. When you reach that point, you enter the world of modern physics. This is where all aspects of metaphysics that can be explained by physics fall under. Of course, the more things we try to prove something right, the more amendments we make. Modern physics too will fall against metaphysics at certain points. This cannot be helped though, knowledge and wisdom will always be counterparts of a larger mechanism. Some will believe the truthfulness of the EPR paradox, while some won't. While one half will state that man possesses free will, the other half asks where in the process of evolution did we gain it (Hawking and Mlodinow, The Grand Design). Some will claim that there is an ultimate purpose of all life, while some will say that there is nothing beyond matter. Stephen Hawking, in an interview with 'The Guardian' newspaper, compared the human brain to a computer, that it will stop working when its components fail. He said: "There is no heaven or afterlife for broken down computers; that is a fairy story for people afraid of the dark."

Whatever be your point of view, it is important to keep moving forward, for I believe there will be the discovery of the truth in due time. There are still many things we need to learn and understand about what goes on within us and around us. So, when Einstein can say, "The man of science is a poor philosopher", Aristotle might say, "The Gods too, are fond of a joke".

What are the different colours of noise?

In Physics, noise has been popularly defined as a disturbance, especially a random and persistent disturbance, that obscures or reduces the clarity of a signal. It is a known fact that white color consists all the colors that can be seen. This holds true in case of sound too, where white noise gets created when sounds of different frequencies reach one's ear. Noise levels and frequency can be charted graphically using the various appropriate colors. The technique of spectral density is used for differentiating noises. This technique is popularly used in fields of electrical engineering and acoustics.

One of the basic noise model used for reflecting the colors of noise is known as Auto-regressive noise model. Colors of noise come in all shades of a rainbow. However, some popular colors of noise include white, pink, red/ brown, blue, green, gray and black. Many physicists assume that there are noise signals with components at all frequencies with a spectral density per unit of sound bandwidth equal to 1/fβ.

Different Colors of Noise

White Noise: The spectral density of white noise can be obtained by putting β=0 in formula 1/fβ which creates a flat spectrum on frequency graph. The sound power of white noise is same at any level of frequency. It is most commonly created in scenes of chaos where it is impossible to perceive a single person's sound or voice. This technique of white noise is commonly used in alarm systems, amplifiers and electrical filters, tinnitus maskers or sound maskers, privacy and sleep enhancers, etc. White noise mechanism is used at times to induce concentration.

Pink Noise: Pink noise is said to lie in between white and red noise. The power density of pink noise falls off at the level of 13 dB per octave or 1/f. For this reason, pink noise is often referred to as 1/f noise. The spectral density of pink noise can be obtained by putting β=1 in formula 1/fβ. Every octave of pink noise contains an equal amount of energy and therefore it is popularly used in sound engineering techniques.

Red Noise: Red Noise is also known as Brown Noise. It usually refers to power density that decreases with increasing frequency. The spectral density of red/ brown noise can be obtained by putting β=2 in formula 1/fβ. The frequencies generated during red noise are said to have a soothing effect and are therefore used to create a relaxing environment and to induce sleep.

Blue Noise: The Power density of blue noise is said to rise at a rate of 3 dB per octave over a finite frequency range. Blue noise is considered ideal for dithering, which is an essential step in music recording. It is also said that retinal cells by nature are arranged in blue noise pattern. This creates a good visual resolution.

Green Noise: With a long-term power spectrum, green noise is considered to the background noise of the whole world. It is soothing in nature and is considered ideal for creating meditative environment.

Gray Noise: When a listener perceives the noise to be equally high at all frequencies, it is usually known as gray noise. In reality though, the frequencies of a gray noise make an inverted A-weighting curve.

Black Noise: Silence is often termed as black noise. The frequency spectrum of black noise is most of the time null, with an exception of some thin bands and spikes. Black noise has been commonly associated with natural calamities such as floods, earthquakes and droughts. Black noise can be denoted with a 1/fβ where β>2.

Colors of noise is a highly technical field that makes a co-relation in fields of sound and color. It is a concept difficult to grasp and comprehend when you begin, however one can gain an expertise in this field gradually. My article is just a tiny input on this subject. I hope this article satisfies your curiosity about the subject and triggers your curiosity to explore more in this field.