Electricity

 about 2500 years ago, a Greek philosopher,  studied the effect of rubbing of two bodies with 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. Amber in Greek is called "electra" and this phenomenon came to be is called "ELECTRICITY".

in 1600 A.D. Dr. Gilbert  discovered that besides amber many other materials like sealing wax, ebonite and glass when rubbed with suitable materials also developed the property of attracting light objects.

POSITIVE AND NEGATIVE CHARGE : 

All matters such as solids and liquids,  gases,  are built up of minute particle called molecules. These molecules can be subdivided into atoms.

all types of atoms are built up  According to modern electronic theory 

of ions having positive electricity called Protons and ions having negative

electricity called electrons. Atoms having no state of electricity are neutrons 

GENERAL STATEMENT : 

(1) A body having so many  of electron (negative electricity) is negatively charged.

 (2) A Body having very low of electrons is positively charged.

ex:  glass rubbed with silk becomes positively charged because by rubbing some of the electrons are withdrawn from glass.

(3) A body having equal positive and negative electricity is said to uncharged body

CURRENT ELECTRICITY : 

Static electricity means electricity at rest. If we join a charged Conductor to another conductor, electricity flows from one to the other. This way, a electric current is produced, which lasts for a moment only. Static electricity is of no use at all.

a continuous current,found that  In about 1790 it is  of electricity could be produced by bringing two dissimilar metals into contact through diluted acid Current electricity can do lot  lot of works .

ELECTRIC CIRCUIT : 

a source of electric pressure OF A battery which is . A resistance R is connected across the battery through switch S. This full arrangement is called electric circuit . when the current flows from +ve terminal passing through resistance R comes to -ve terminal.

 CURRENT . Flow of electrons in conductor is called electric current, symbol OF current is I.  unit of current is Ampere and measured by ampere meter.

VOLTAGE : electrical pressure between two points is also called as Voltage, Electromotive force (E.M.F.) or potential difference (P.D.). It is the pressure that moves the electrons to flow in conductor. Its symbol is V. the unit of voltage is volt and measured by a voltmeter.

RESISTANCE : the substance which do not allow to flow of electron through it self that's called resistance . unit of resistance in ohm and measure by ohm meter .

ELECTRON THEORY : 

Benjamin Franklin in  the year 1749 , proposed that the electrification of the bodies is due to electric fluid which combines with them in different degrees.a certain quantity of fluid  When the body is neutral has . The body becomes positively charged if the is excess of electric fluid and becomes negatively charged if the quantity electric fluid decreases than its normal quantity (which makes it neutral). Thu before rubbing, the ebonite rod is neutral and when it is rubbed with fur, certain amount of fluid passes from the rod to fur so that the rod become negatively charged and the fur becomes positively charged, but the total quantity of fluid remains the same.

 MODERN THEORY . The ELECTRON THEORY' is also known as  modern theory  ' This theory not only explains about attraction, repulsion and two kinds of electrification in electrostatics; but also gives 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. The matter defined as the substance which possesses weight and

occupies space and can be in any of three forms solid, liquid or gaseous. The matter consists of three ingredients :

All matter, according to electron theory, is fundamentally the same; thus copper, iron, aluminium, etc., all will have the same basic ingredients  arranged in a different manner. In other words, if the structure of aluminium 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.

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 centre which consists of positrons and neutrons. As one positron and one neutron got together, it is called 'proton'. As all the elements have more neutrons than positrons, so the positron do not exit themselves, but from protons and hence the nucleus has protons and excess of neutrons. Since the positron having an opposite charge combines with a neutron having no charge, the charge of proton is positive. The nucleus spins on it own axis. The number of positrons in an atom corresponds to an 'atomic number . 

The negative charges ingredients of an atom, i.e., electrons are arranged

in shells. Each of the electrons rotates round the nucleus in 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 clockwise direction and

others move anti-clockwise . Thus, the electrons move round

the nucleus and rotate on their own axis also: this conforms to the solar system

with the planets moving round the sun at the centre 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. 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 'K' shell and

has a maximum number of two electrons ; the second 'L' shell has maximum

number of 8 electrons : the third 'M' shell has maximum number of 18 electrons and the fourth 'N' shell has maximum number of 32 electrons.

 It is importan

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 .

LAW OF CONSERVATION OF ENERGY

The energy can be defined as the capacity to do work. There is a law of It has been known that all substances are composed of matter and energy 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 sea rises up in vapour form due to heat energy of 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 a certain energy is supplied to 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, the positive change on protons predominates. The glass becomes positively charged and the silk now possesses excess number of electrons than the normal, so it becomes negatively charged. The energy supplied to displace the electrons from the glass is converted in the form of field of force surrounding the glass rod.