Electronics

ELECTRONICS
It is the study based on the flow of electrons to design circuits, devices and systems using resisters, capacitors, semiconductors, vacuum tubes etc

ELECTRICITY
It is the energy given by the:
    Batteries
    Generators
    Solar cells etc.  
Unit of electricity is kilowatt/hour.

ORIGIN
Electrons, electricity, electronics all begin with “ELECTR—” originate from Greek word “ELECTOR” meaning “Beaming Sun” also elector is used for “AMBER” (Arabic: a jewel quality fossilized resin)

CHARGE ON ELECTRON: 1.6 x (10)-19 coulombs.

Where does electricity come from?

    To know we need to understand about atoms and their structure
    All matters is made up of atoms
    Element is a substance that cannot be broken into other substances
    Smallest particle of an element is atom
    Different elements have different atoms
    Atom is like a little solar system

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    Electron carries negative charge
    Proton carries positive charge
    Neutron carries no charge
    Electrons live in the orbital of the atom

VALANCE ELECTRON
    Electrons with highest energy levels exist in the outer most shell.
    These are far away from the nucleus.
    These are loosely bound to nucleus.
    These electrons take part in chemical reaction.
    These electrons make bond with other atoms.

VALANCE BAND
It is the energy band due to valance electrons.

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2 electrons in the inner shell
4 electrons in the outer most shell
So carbon has 4 valence electrons

ELECTRON ENERGY LEVELS IN AN ATOM

    Electrons near to nucleus have less energy
    Electrons away from the nucleus have high energy
    Each electron have has associated energy

ENERGY BANDS
    Electrons in the same orbital or shell have small differences in energy levels
    Such electrons are grouped in energy bands (see fig below)

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CONDUCTION BANDS IN ATOMS

    Electrons in VB is loosely bound to atom
    Such electrons when gets some energy, it can leave VB and get free from atom
    Such electron freely move in the material and not bound to atom
    Energy level of such electrons make conduction band (band of energy due to free electrons)

TYPES OF MATERIAL ON BASIS OF ELECTRICAL PROPERTIES
    CONDUCTORS
    INSULATORS
    SEMI CONDUCTORS

ENERGY GAP

It is the energy difference between valance band and conduction band of an atom.
    Energy gap determines the electrical properties
    Energy gap determines if material would be (CONDUCTOR, INSULATOR, SEMICONDUCTOR)

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CONDUCTOR

    Single element  materials are best conductors
1.    COPPER
2.    SILVER
3.    ALUMINIUM
4.    GOLD
    All these have only one valence electron which is very loosely bound to the atom, and very easily gets free at room temperature
    A conductors have a huge num of free electrons
    When these electrons move in one direction it make up the current or electronic current

APPLICATIONS OF CURRENT

    A medium to carry telecommunication signals
    A medium to carry electrical power or energy from one point to another

INSULATORS
    In insulators, energy gap between valance band and conduction band is very wide
    Valance electrons do not jump into the conduction band except under break down conditions where very high voltage are applied across the material
    Valance band is completely filled
    It do not conduct electricity
    It has very high resistance 
    SOME INSULATORS
1.    rubber
2.    wood
3.    plastic

SEMI CONDUCTORS

    Energy gap is not wide
    With little energy support, electrons can jump from VB to CB
    SOME SEMI CONDUTORS
1.    silicon
2.    germanium
These semi conductors are mostly used in electronics

 

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