Static Electricity
Thales, a Greek philosopher, of about 2,500 years ago, studied the effect of rubbing of two bodies against each other and found that amber*, when rubbed with fur or flannel, acquired the property of attracting light objects such as pieces of paper, pitch, feathers, etc. In Greek, amber is known as 'Electra'and this phenomenon came to be known as 'ELECTRICITY'
Dr.Gilbert, in the year 1600 AD., discovered that besides amber, many other materials like sealing wax, ebonite, and glass, when rubbed against suitable material, also developed the property of attracting light objects,
ELECTRON THEORY
There are several theories of Electrification that have been advanced to prove the phenomenon of electrification .
Benjamin Franklin's One-Fluid Theory.
In the year 1749, Benjamin franklin proposed that the electrification of the bodies is due to electric fluid which combines with them in different degrees. When the body is neutral it has a certain quantity of fluid. The body becomes positively charged if there is excess electric fluid and becomes negatively charged if the quantity of electric fluid decreases than its normal quantity ( which makes it neutral ). Thus, before rubbing, the ebonite rod is neutral and when it is rubbed with fur, a certain amount of fluid passes from the rod to fur so that the rod becomes negatively charged and the fur becomes positively charged, but the total quantity of this remains the same The theory emphasizes that there are only two states of Electricity and not two kinds of electricity.
Summer's Two - Fluid Theory.
According to Summer electrification is due to two electric fluids: positive and negative. A neutral y possesses these fluids in equal quantities. When two bodies ( ebonite and flannel ) are rubbed the negative fluid goes to one ( to ebonite ) and the positive fluid goes to the other ( to flannel ). The theory undoubtedly proves that the two similar fluids repel each other and unlike fluids attract, and it also proves that there is the simultaneous development of the kind of electrification.
Modern Theory .
The modern theory is also known as ' ELECTRON THEORY ". This theory not only explains attraction, repulsion, and two kinds of electrification in electrostatics; but also gives a clear conception of voltage, resistance, insulation, induced voltage, and magnetism. To follow this theory, let us consider that the whole of the universe is composed of two things - one is matter and the other is energy. Matter. Matter is defined as anything which possesses weight and occupies space and can be in any of three forms solid, liquid, or gaseous. The matter consists of three ingredients :
Positrons ( Protons )
These are the particles having a positive charge. ( it )
Neutrons.
These are the particles having no charge and are neutral and contribute practically towards whole the weight of mater
Electrons
These have an opposite charge to that of positrons. These possess negative charges and are very light in weight. All matter, according to electron theory, is fundamentally the same; thus copper, iron, aluminum, etc., all will have the same basic ingredients ( positrons, neutrons, and electrons ) arranged in a different manner. In other words, if the structure of aluminum is examined it will be found to have a certain specified number of positrons, neutrons, and electrons arranged in a definite manner, and if the structure of iron is examined it will also have the positrons, neutrons, and electrons but their number will be, different and arranged in a different manner. 5 A matter can be said to be composed of all particles called ' atom ' and the atom itself is composed of positrons and electrons arranged in a particular fashion known as the structure of an atom. An atom has a nucleus at the center which consists of positrons and neutrons. As one positron and one neutron got together, it is called a' proton '. As all the elements have more neutrons than positrons, so the positron does not exit themselves, but from protons and hence the nucleus has protons and excess neutrons. Since the positron having an opposite charge combines with a neutron having no charge, the charge of the proton is positive. The nucleus spins on its own axis. The number of positrons in an atom corresponds to an ' atomic number. The chief characteristics of the electron, proton, and neutron are given below :
| S.no | Name of atomic ingredients | Electrical charge is coulombs | Mass of kilograms |
| 1 | Electron | 9.107x10^-31 | |
| 2 | Proton | -1.602x10^-19 | +1.6727x10^-27 |
| 3 | Neutron | +1.602x10^-19 | +1.6751x10^-27 |
The negative charge ingredients of an atom, i.e., electrons are arranged in shells. Each of the electrons rotates around the nucleus in an elliptical ring. After one complete rotation, the plane of the rotation of the electron shifts a few degrees so that now it will form another new ring and after its completion, another ring will be formed, then another, and so on, and it will trace a sphere. Moreover, in a shell, some of the electrons move in a clockwise direction and others move anti-clockwise as shown in Fig . 1. Thus, the electrons move around the nucleus and rotate on their own axis also this conforms to the solar system with the planets moving round the sun at the center and revolving on their own axis. These electrons retain their circular path as there is always a balance of centrifugal force due to their circular motion and the attraction between the electrons and protons is as represented in Fig . 1. The electrons in the second shell will be farther away from the nucleus so attraction will be less; also the electrons in the second shell move with lesser speed resulting in a lesser centrifugal force, thus, there always remains a balance between two forces acting on electron. The first shell occupied by electrons is known as the ' K ' shell and has a maximum number of two electrons; the second ' L ' shell has a maximum number of 8 electrons the third ' M ' shell has a maximum number of 18 electrons, and the fourth ' N ' shell has a maximum number of 32 electrons. It is important to remember that it is not necessary for the electrons to complete their previous shell before they can occupy the next shell. The atomic structures of copper and silver are the examples as given in Fig . 2
Law of Conservation of Energy It has been known that all substances are composed of matter and energy .. Energy can be defined as the capacity to do work. There is a law of conservation of energy, according to which the energy can neither be created nor can it be destroyed, but it can be converted from one form to the other.
For example, the water from the sea rises up in vapor form due to the heat energy of the sun and forms clouds. The clouds, due to their high position, possess potential energy and when the rain falls, this water forms streams, waterfalls, and then rivers. Thus, the potential energy is converted into kinetic energy. The kinetic energy may be used to turn the wheel of a turbine, so changing kinetic energy to mechanical energy and if an alternator is coupled to the turbine, the mechanical energy is converted into electrical energy which, in turn, can again be converted to heat energy.
Positive and Negative Electricity
The electrons in the structure of an atom do not always remain in the same atom but can be detached from it when certain energy is supplied t it. Thus, when silk is rubbed on a glass rod, due to the friction ( or heat energy the electrons from the glass rod, pass to the silk. The interchanging of electrons leaves the glass in excess of protons, and the positive change on proton predominates. The glass becomes positively charged and the silk now possesses = an excess number of electrons than the normal, so it becomes negatively charged The energy supplied to displace the electrons from the glass is converted into the form of a field of force surrounding the glass rod
Do You Know?
1.Speed of Electricity ( Electrons ) is 2,97,842 km ( 1,86,000 miles ) per second which is more than the speed of sound .
2. In India usually 11000 volts A.C. is produced . This voltage can be further reduced ( 440 V ) for load and increased 33000 , 66000 V , 132000 V etc. ) for transmission .
3. In India the supply frequency is 50 cycles per second . 4. In your house all the lamps , tubes , heaters , etc. , are connected in parallel
