the main page the main page the main page the main page

the Electricity and magnetism

the Science and technics
 
ru - ua - en - fr - by - de - es

In olden time the electric phenomena in the form of a lightning and a thunder caused people terrible fear. Later we have learnt to use an electricity for the needs. And magnetism, is no time no more than the strange phenomenon, plays today one of the major roles in the huge generators providing us with energy.

the Electricity and magnetism Some fabrics is strong elektrizujutsja when the clothes sewed from them remove through a head. Sometimes the charge happens so powerful that it is possible to hear a crash of electric sparks, and in a dark premise - even to see them. These sparks represent a lightning in a miniature and, like last, result from the sharp electric category. During a thunder-storm the electrified cloud is discharged, the large quantity of energy in the form of light and heat is thus allocated. Light is perceived by us as lightning flashes, and the thermal stream causes sudden, vzryvopodobnoe air expansion - and we hear thunder peals. All objects surrounding us contain millions the electric charges consisting of particles, being in atoms - bases of all matter. The central part, or a kernel, the majority of atoms includes two kinds of particles: Neutrons and protons. Neutrons have no electric charge while protons bear in themselves a positive charge. Round a kernel one more particles - elektrony, having a negative charge rotate. As a rule, each atom has identical quantity of protons and elektronov, whose equal on size, but opposite charges counterbalance each other. As a result we do not feel any charge, and the substance is considered not charged. However, if we somehow break this balance the given object will possess the general positive or negative charge depending on what particles in it remains more - protons or elektronov.


the Electricity and a friction

Various materials sometimes elektrizujutsja at a friction the friend about the friend as thus there is a transition elektronov from one material in another. For example, if you use a plastic hairbrush, elektrony hair passes to it. As a result the hairbrush appears negatively charged, and hair have a positive charge as now in them there are more than protons, than elektronov. The charged objects draw not charged and consequently small slices of a paper stick to a hairbrush.


the Attraction and pushing away

The Charged objects either draw, or push away each other. If they have opposite charges between them force of an attraction operates. But if at them the charges with the same name then force of pushing away takes place.

It is considered that the object electrified at the expense of a friction, possesses a static electricity as the charge can remain in it is almost infinite. Such object remains charged until in it the balance of positive and negative particles will not be restored. It is reached by possibility granting "яхЁх=хърэш " the charged particles from the given object or in it. For example, the object which has received a negative charge in view of transfer to it of additional quantity elektronov can be discharged if to allow superfluous elektronam to leave again it. And positively charged object as a result of quantity loss elektronov can be discharged, having given the chance lacking elektronam to return back. Any similar movement of the charged particles is called as an electric current.


Conductors

The Substances allowing a current to pass through them, are called as conductors. Metals and graphite, and also a usual version of carbon are good conductors of an electricity. To materials which usually do not instal electrical equipment, amber, oil, wax, glass, a paper and plastic concern. Such materials are called dielektrikami.

In a XVIII-th century many scientists made experiments with an electricity, using the cars providing a friction of one material about another for reception of a powerful electric charge. However such charge quickly disappeared as a result of sudden emission of a current at conductor connection to the equipment. The source, capable to make stable enough current during longer period of time would be much more suitable for many experiences. In 1790th years the Italian scientist Alessandro Volta has found the necessary decision - he has invented a galvanic cell and the battery.


Elements and chains

The Galvanic cell will transform chemical energy to an electricity. These elements often connect with each other or group for reception of more powerful source of the electric power in connection points, or poles. Such connections are called batteries. However individual elements also often call batteries. The chain consists of an electricity source (such as the battery) and current ways on which the current can proceed from one pole of a source to another. The electrocurrent represents a stream elektronov; it can be compared to water stream, moving on a pipe. To force water a leak on a pipe, it is necessary to create pressure, the same needs to be made with elektronami to force them to proceed, but to a wire. Such electric pressure, or the pressure created, for example, by the battery, is measured in voltah, and obrazuemyj thus a current - in amperes. The water stream received at certain pressure, depends on a kind of a used pipe. For example, the long and narrow pipe will show resistance to water stream in it. And the long and thin wire will render bolshee resistance to an electrocurrent, than a short and thick wire from this a material.


Resistance

The Unit of measure of electric resistance is the Ohm. As copper has rather low resistance and, hence, is a good conductor of an electricity, it is widely applied in cables. Still the best conductor is silver, but it is too expensive for wide application. In some chains elements which are intentionally made with high resistance are used. Such devices - resistors - are often used for restriction of course of a current on separate sites of electronic schemes.


Magnetism

.

It is considered that the Greek philosopher Fales Miletsky the first studied a strange attraction magnetic iron ore of usual iron. It occurred about 600 years BC, and have passed a century before magnetism has found practical application in the form of a magnetic compass. Possibly, in China approximately by 200 year d.C. already there was an imperfect sample of a magnetic compass, however in Europe it has appeared not earlier than 1200

Throughout many centuries nobody could solve secret why the piece of natural magnetic iron ore (if he could move freely) always specified the same direction. Today we know that iron and other magnetic materials consist of the tiny magnetised particles named domains. Usually they settle down in various directions, and metal does not show as a whole any magnetic properties. If domains are built in such a manner that all of them are directed to one party metal is magnetised and draws other pieces of iron.


Two poles

All magnets such have one common feature: their magnetisation is concentrated on two sites which northern and southern poles of a magnet are called. They have received such name because, when the magnet can freely rotate (in the suspended or floating condition), these parts of a magnet turn in a direction of Northern and southern poles of the Earth, which in itself is a huge magnet. The principle of action of a magnetic compass consists in it. Both poles of a magnet draw not magnetised iron. But if to approach two magnets, northern pole of one of them will draw South Pole of another. In other words, heteronymic poles are drawn. And on the contrary - northern two poles will push away each other the same as also two southern. Therefore say that the poles with the same name mutually make a start. In that case, however, can seem strange that northern pole of a magnet is inclined to turn towards the North Pole of the Earth. It occurs because the magnetic north (a magnetic pole near to area which we name the North Pole) actually is a southern magnetic pole.


Between an electricity and magnetism there is a close connection, but about it it became known only in 1819 when the Danish professor of physics Hans Ersted has shown to the students some properties of an electricity.


Otkrytie Ersteda

Ersted has connected a wire to battery poles to show that it heats up at passage through it of a strong electric current. However there was something absolutely unexpected. When it has connected a wire to the battery, the arrow of the compass which was nearby has deviated and any more did not specify in the north. Ersted has understood that the electrocurrent passing through a wire created the magnetism influencing a compass. So it has opened one of the major phenomena in a science - electromagnetism.


Electromagnetism

The Current passing through a wire, creates rather weak magnetism. But soon scientists have found a way of strengthening of this phenomenon. More expressed magnetic properties could be received, having made a wire winding in the form of the coil and having reeled up it round an iron core. Such device is called as an electromagnet.


Engines and generators

Engines and generators If a wire which is near to a constant magnet to connect to the battery, it can move under the influence of created magnetism. In 1821 English scientist Michael Faradej has constructed the simple car in which tokonesushchy the wire moved round a constant magnet.

Ersted has shown that the electricity can create magnetism, and Faradej has thought that it is possible to use magnetism for electricity reception. It has shown for the first time it in 1831 when has received an electricity, moving a rod magnet in the wire coil. It also has shown that the result remains invariable irrespective of, whether the magnet or the coil moved. This principle is applied in the modern generators supplying with the electric power our houses, shops, offices and factories.