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We live in an ocean of electric and magnetic fields. Just like when the ocean is calm, these fields can be more or less stable, but come a storm, and they can become very rough. Free Download Tmnt 2 Gba.

From childhood we know that a magnetized compass needle points to the North Geomagnetic Pole of the Earth. The invention of a compass played a significant role in our development as humans. This was especially true with the development of marine navigation. Compared to the magnetic field, the electric field of the Earth does not display its properties, and it is generally difficult to detect without specialized equipment.

We can, however, see the effects of the electric field when we brush a plastic comb through the washed and dried hair: it is due to the electric field that the hair rises to follow the brush. A similar effect happens when we move the same comb over some small pieces of paper or plastic film, and these pieces overcome gravity, jump up, and stick to the comb. Yet, come an electrical storm, and we can feel its approach without any equipment. We see the flashes of the distant lightning and hear the thunder, which announces the coming storm. It causes the interference with the radio and television broadcasting, and the lightning may even damage the radio and electronic devices.

New York An example is the black-out in New York in 1977, when most of the city had no electric power after a series of lightnings hit several different power lines. Geomagnetic storms in space can also cause disruptions of electric supplies in a city, a region, and sometimes even an entire country. An example is the black-out in Quebec in 1989. These storms can also cause disruption in cross-continent telegraph service as during the Carrington event that happened in 1859 as a result of a solar storm.

We should note, however, that these geomagnetic disturbances of the Earth's magnetic field are generally less than 1% of the total amount of notable magnetic disturbances. As far as we understand at the moment, the changes of the electric and the magnetic fields in time create electromagnetic fields that can be viewed as single, integral entities, which change with either a lower or a higher frequency. The electromagnetic spectrum of these frequencies is wide, from the infra low frequencies of a fraction of a hertz to gamma radiation with frequency in exahertz. Here is a curious but little-known fact: the power of the signal, emitted by the Earth in the narrow range of frequencies used for television and radio broadcasting and by communication satellites exceeds the power of solar radiation.

Some radio astronomers suggest that we search for extraterrestrial civilizations based on this factor. Other scientists, on the other hand, consider this fact to be proof of our current incompetency in managing our natural energy resources and proof that our current technology has a long way to go. One of the most important characteristics of an electric (as well as a magnetic) field is its strength. When it is exceeded for a specific medium (for example 30 kV/cm for air), an electrical breakdown occurs, manifested by discharge in the form of sparks or even an arc. An example of such a discharge is in electric lighters. The power of this discharge in the electric lighters is so small, that its energy is only enough for heating the gas to its temperature of combustion. Lightning and the Ionosphere The power of a single lightning at average voltage of 20 million volts and current of 20 thousand amperes can be about 200 million kilowatts.

This number takes into account the fact that when the lightning strikes, the voltage drops from the maximum value to zero. One large thunderstorm produces enough lightning power to address the energy needs of the entire population of the USA for twenty minutes. Given the fact that about 2000 thunder storms happen on Earth simultaneously, a very attractive prospect is to be able to use the electricity produced in the ionosphere of the Earth. A number of projects exists aimed at harnessing lightning power using specialized lightning rods or by initializing the discharge that occurs when the lightning strikes. We also have technologies for artificially triggering lightning discharge. This is done by launching small rockets or flying kites that are connected to Earth with conductors.

Some promising ongoing research includes technologies, which trigger lighting by creating conductive channels by means of ionizing the atmosphere using powerful lasers or microwave radiation. This minimizes costs because we do not need to worry about the cost of conductors, which are evaporated when hit by lightning. The physics behind the aurora borealis is the same as for the glow of gas-discharge lamps in an electromagnetic field, as we can see in this illustration. Light is emitted as a result of the ionization and excitation of atoms of atmospheric gases and their subsequent return to their normal state.

Perhaps one day we can make the dream of the electricity genius Nikola Tesla, a Serbian-born American scientist, become reality. He wanted to be able to harvest electric energy in a specified amount and from any location on Earth, even from the atmosphere. During his experiments on generating lightning in his lab in Colorado Springs in 1889 he managed to generate and transmit electric energy of such high voltage that some horses in the neighborhood fell down due to the electric shock that they received through their metal horse shoes. Butterflies were flying surrounded by St.

Elmo’s lights, pedestrians walked through sparks, and sparks also flew out of water taps. Perhaps it is due to such experiments that during his time people considered him crazy and dangerous, an epitome of the mad scientist. No wonder they say that there is a fine line between genius and insanity.

Some History. A visualization of the field lines of an electric field using potassium permanganate. 30 V DC voltage is applied to the two electrodes, which stand on pieces of filter paper soaked in sodium chloride The law of interactions between electric charges, discovered by Charles-Augustin de Coulomb in 1785, known as Coulomb’s law of electrostatic interaction, gave physicists tools to calculate the properties of these interactions. This law is very similar to Newton’s law of universal gravitation, which was discovered earlier.

One significant difference is that Coulomb’s law considers the interaction of different charges, negative and positive, while the law of gravitation only talks about one type of interaction, the one where bodies can only be attracted to each other. Similarly to Newton, who could not explain the reason for gravity, Coulomb also did not explain the reason for the interaction between the electric charges.

Some of the best scientists of the time suggested various hypothesis of the nature of these forces, including the theories of short-range and long-range interaction. The former assumed that an intermediate agent known as world ether was present and it was believed to have very unusual properties, for example very high elasticity with extremely low density and viscosity. This was because at the time scientists believed that the forces required a specific medium, and in this case the medium was thought to be a liquid. We stopped studying these medium very recently, in the 20th century, thanks to the experiments of the American physicist Albert Michelson, and thanks to Albert Einstein developing his theory of relativity. Visualization of field lines using motor oil and semolina. Oil and semolina are dielectrics. When the DC voltage of 30 kV is applied, the semolina particles align along the field lines, which extend out from the center to the ring electrode.

Research of the eminent British physicists Michael Faraday and James Clerk Maxwell in the end of the 19th century was fundamental in moving the field in the right direction. Michael Faraday showed a link between the magnetic and the electric fields when he introduced the concept of a field and created a visualization of this interaction using lines of force.

The modern way of depicting electromagnetic and other vector fields is by using field lines. Similarly to the visualization of the field lines of a magnetic field, which is created by spreading metal filings in the magnetic field produced by a magnet, Faraday created a visualization of an electric field by placing crystals of dielectric quinine in a viscous liquid, which in his case was castor oil. These crystals created interesting chains near charged objects; their shape depended on the distribution of charges.

The main contribution that Faraday made was introducing the notion that electric charges do not act upon each other directly. Each charge creates an electric field around it, and a magnetic one as well if it is moving. Download Naruto Rise Of A Ninja Pc Tpba.

The electromagnetism phenomena are in fact caused by the change in the number of field lines, enclosed by a given outline. A visualization of field lines of an electric field using motor oil and semolina, for two linear electrodes with the voltage of 30 kV Here the number of lines of force refers to the strength of the electric or the magnetic field. A famous fellow countryman of Faraday, J. Maxwell summarized his ideas quantitatively and mathematically, which is extremely important in physics. His equations became fundamental in studying both theoretical and practical electrodynamics.

His work put a stop on the study of long range interaction, because his studies predicted the finite speed of the spread of electromagnetic interaction in vacuum. Using Maxwell’s work, the genius physicist of the 20th century, Albert Einstein, later postulated the finite nature of the speed of light. He built his special and general theories of relativity on this underlying premise. Modern physics gives different meaning to the notion of action at a distance. The forces, which decrease with distance according to the inverse square law (r -n) are considered to be forces that act long-distance. They include gravity and electromagnetic forces, which decrease proportionally to the inverse square of distance, and act on objects in the world under regular conditions. The atomic world has different forces, which rapidly decrease with distance.

They include the strong and the weak interactions, which act on objects in the world of elementary particles. Defining the Strength of an Electric Field The strength of an electric field is a vector. It characterizes the electric field at a given point and equals to the ratio of the magnitude of the force that acts upon a stationary electric charge, which is located at this point, and the magnitude of the charge. It is denoted with the letter E and calculated using the formula: E = F/ q where E is the vector of the strength of electric field, F is the vector of the force, applied to the point charge, and q is the charge of the object. Each point in space has its own value for the strength of the electric field vector, because the electric field can change with time. Therefore, when we describe the strength of the electric field vector we include not only the coordinates for space but also for time. E = f ( x, y, z, t) In SI the strength of electric field is measured in volts per meter (V/m) or in newtons per coulomb (N/C).

In addition units derived from volts per meter are also used, including volts per centimeter (V/cm). In electrical engineering kilovolt per meter (kV/m) and kilovolt per centimeter (kV/cm) are also used. The countries that do not use the metric system for distance use volts per inch (V/in) instead.

The Physics of the Strength of an Electric Field As we discussed earlier, the calculations for vector electric fields (that is, calculating strength of electric fields) of physical objects are done using Maxwell’s equations for electrostatics, and using Gauss’ divergence theorem, which is part of Maxwell’s equations. As we perform these calculations we need to keep in mind the peculiarities of the behaviors of electric fields in different medias, since their manifestations depend on the conductivity of the material or substance. Electric Field in Dielectrics.

An electret condenser microphone for iPhone When an electric field of high strength is acting upon an object made of a dielectric, the polar molecules inside this object that were previously oriented at random usually reorient themselves towards the electric field. This is called polarization. Even when the electric field stops acting upon the object, this new orientation is preserved. To return the molecules back to their initial state we need to apply a field that has the opposite orientation relative to this object. This phenomenon is called dielectric hysteresis.

There are other ways to bring the dielectric to its original state. The most common way includes heating of the object, which causes a phase transition. These types of materials are called ferroelectrics. They include materials, which have a very high dielectric hysteresis loop and can stay polarized for a long time. We call these materials electrets and we can think of them as of equivalents of permanent magnets, which create a permanent electric field. Hysteresis in Ferroelectrics We should note that ferroelectrics have nothing to do with iron.

They were so named because ferroelectricity phenomenon, which is the property of ferroelectrics is similar to ferromagnetism. When an alternating electric field is acting upon the molecules of a dielectric material, the molecules start acting differently. They constantly realign their charges with each half period of the field applied to them. We know about these behaviors thanks to J. Maxwell, who introduced the notion of displacement current.

This phenomenon is manifested when alternating current is applied to bound charges, namely the electrons and the nuclei of atoms dielectric molecules. The electric field makes them vibrate relative to the center of the molecule. Electric Field on the Surface of Metals The effect of an electric field on metals is quite different. Because metals have free charges (electrons) relative to any electric or electromagnetic field, they become similar to an optic mirror that reflects light. Directional parabolic satellite antennas Most of the directional antennas for radio signals are built using this principle. Regardless of the structure of the antenna it always has the major component, the deflector, which can significantly amplify the signal and thus improve the quality of signal detection. This deflector can be of any shape, it can even be very similar to a mirror, shaped as a parabolic deflector of an antenna for satellite signals.

Essentially, the deflector can be a unit that concentrates the electric field strength. Because metals reflect electric and electromagnetic fields, this property is used in the electrostatic protection cage, known as the Faraday cage or shield. The metals of these cages completely isolate the space inside them from the effects of the electric and the electromagnetic fields. The genius of electricity Nikola Tesla knew well about this property and surprised his unsuspecting audiences by appearing inside a cage surrounded by a halo of electric discharges, which were generated by a resonant transformer.

We now call it a Tesla transformer or a Tesla coil. Tesla coil and a human 'hamster wheel' in the Canada Science and Technology Museum in Ottawa. Museum visitors have to generate about 100 watts of energy in order to create a spark. In 1997 Austin Richards, a physicist from California created flexible protective gear that shields the wearer from the electrostatic discharges from a Tesla coil.

Thanks to this invention he has been performing since 1998 as Dr. Megavolt in the show 'The Burning Man'.

Modern conference rooms meant for secret meetings are also built using the Faraday cage. We should mention that the researchers from the KGB’s secret laboratories were able to get around this technology at some point in history. They had bugs built as isolated units into the load bearing walls of the building.

This was done under the assumption that they will generate a response modulated signal when exposed to radiation, and will allow to record the secrets of the American diplomats. Examples of Systems and Devices that Use an Electric Field. The room where an electronic microscope is used has to have good sound insulation. Because of this requirement it often resembles a recording studio, minus the window. There are numerous examples of using the electric field, and there are just as many examples of shielding from the effects of the electric field. Scanning Tunneling Microscope (STM) One of the principles of operation of a scanning tunneling microscope (STM) is the creation of an electric field between the sample and the probe of such strength that it exceeds the work function of the electrons leaving the sample.

This is done by creating a difference of potentials between the probe and the sample, and by moving them close together so that there is less than 1 nanometer between them. We can then map the surface of the sample and get an idea about its profile by measuring the tunneling currant while moving the probe over the surface of the sample. Hundreds of weather balloons are sent into the ionosphere by the meteorological stations across the globe. They are attached to hydrogen-filled balloons.

The probes like the one in the picture from the Canada Science and Technology Museum were used in the mid-twentieth century. Because this device is very sensitive to mechanical vibrations, the rooms that house scanning tunneling microscopes have special properties.

One of them is good sound insulation — the surface of the floors, ceilings, and windows has to be covered with materials, which absorb vibrations caused by sound waves. Measuring and Alerting Devices The labor protection requirements classify premises according to the strength of the electric field present there. Depending on this level the amount of time spent on these premises is strictly regulated. Strength of the electric field is measured using various devices. Meteorologists keep track of the electric field of the Earth by measuring its strength both on the surface and in various atmospheric layers, using weather balloons.

Electricians who work with high voltage power lines use various notification devices to monitor the strength of the electric field. These devices give notice when the values reach the critical point that is considered dangerous.

Electrostatic and Electromagnetic Protection As far as back in the 1836 Faraday used a shielding device that he invented. It was designed to protect the environment in which he performed chemical experiments from the effect of the electrostatic. Now this device is known as a Faraday cage. The enclosure can be made of a solid perforated conductive material or from conductive mesh.

A microwave oven is, in fact, a Faraday cage, except that it blocks internal instead of external radiation. The bottom photograph shows that the size of the grid cell is about 3 mm. It is much smaller than the wavelength of electromagnetic radiation of the microwave oven, which is about 12 cm.

The same device can be successfully used to block electromagnetic radiation with the wave length significantly longer than the size of mesh cells or perforations in the enclosure made of a sheet of perforated metal. Modern technology uses Faraday cages in physics labs and experimental setups, in analytic chemistry labs, and in measuring devices. They are also installed in conference rooms equipped for closed secret meetings, and were even installed in the room used for the meeting of the conclave of cardinals in the Vatican, during the last election of the Pope. Faraday cages are also used in some diagnostics centers and hospitals, for example in rooms where MRI is performed. Even the common microwave oven that most of us have at home is a Faraday cage.

The transparent window that allows us to look inside is not, in fact, penetrable by microwave radiation because it is covered with a conductive mesh, whose cells are much smaller than the wavelength of electromagnetic radiation used in the oven. Screening of connector wires and coaxial cables is widely used in radio electronics, computer engineering, and communication technologies for shielding the external electromagnetic radiation from interfering with the work of the cables, and also for preventing the internal electromagnetic radiation from escaping to the environment. We can also call these shields Faraday cages. Experiments on the Effects of the Electric Field on Metals and Gases.

Lighting a neon lamp with the help of a plasma globe Given that precise measurements of the strength of the electric field require specialized devices, here we will look at the properties of an electric field using simple available devices. Plasma Globe Let us use a neon, a fluorescent, or any other gas-discharge lamp filled with inert gas as an indicator of the strength of the electric field that we are measuring. We can use a plasma globe to generate an electric field. It can generate an alternating electric field of high strength with a frequency of about 25 kHz.

If we touch the plasma globe with our fingers, the plasma threads are concentrated around the area that we touch If we place our lamp near the insulating sphere of the plasma globe, it will start to glow. This happens even when the lamp is broken, as long as its tube is intact. The glow is an indicator of the presence of the electric field.

This glow is possible because the electromagnetic field penetrates the glass envelopes of both lamps. The electric field excites the electrons of the upper envelope of gas atoms, and when these atoms return to their normal state they generate light. If you bring your hand close to the plasma globe, the plasma thread will grow thicker, because at the point where the hand is the closest to the lamp the strength of the electric field is increased. Using an Oscilloscope to Estimate the Strength of an Electric Field Let us connect a probe made of a piece of wire of about 15 cm to the input of the oscilloscope. Now let us bring this probe close to a plasma globe. We can see oscillations with the same frequency of 25 kHz and the amplitude of 25 volts.

A high alternating voltage is applied to the electrode of the globe. This generates a variable electric field in the space around the area. We can see that as we increase the distance between the lamp and the probe, the range of the signal decreases as in images 1 to 3. The decrease in the amplitude of the signal displayed on the oscilloscope tells us that the strength of the electric field decreases with distance.

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