Download Int. to Basic Electronics - Kashif Bashir

Electricity
Kashif Bashir
Email: [email protected]
Web:www.kashifpaf.greatnow.com
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Introduction
• Electricity is an invisible force that can produce heat, light, and
motion.
• Electricity can be explained in terms of electric charge, current
and voltage.
• All the materials contain two basic particles of electric charge:
electron(-ve charge) and proton(+ve charge).
• Separate and opposite charges at the two terminals, electric
energy can be supplied to a circuit connected to the battery.
• An atom is the smallest particle of the basic elements that form
solid,liquids, and gases we know as physical substances.
• In an atom all the protons are in the nucleus, while all the
electrons are in one or more outside ring.
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•Such electrons that can move freely from one atom to atom to
the next are often called free electrons. The movement of free
electrons that provides electric current in a metal conductor.
•When electrons can move easily from atom to atom in a
material, it is a conductor.
• In general all the metals are good
conductors, with silver the best and copper
second.
•A material with atoms in which the electrons
tend to stay in their own orbits is an insulator b/c it cannot
conduct electricity very easily.i.e glass, plastic, rubber etc.
Carbon can be considered a semiconductor, conducting less
then the metal conductors but more then the insulators.
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Germanium, Silicon.
•An element is defined as a substance that cannot be
decomposed any further by chemical action.
•A group of two or more atoms forms a molecule.i.e H2O.
Structure of the Atom:
•Energy levels
•Atomic Number
•Electron Valence
•Coulomb unit of electric charge(6.25 x 1018 e- or P+).
•Charges of opposite polarity attract and charges of the same
polarity repel.
•Potential refers to possibility of doing work.When we consider
two unlike charges, they have
a difference of potential.
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•The volt is measure of the work needed to move an electric
charge. when 0.7376 foot-pound of work is required to move
6.25 x 1018 electrons b/w two points, each with its own charge,
the potential difference is 1 V.
•Voltage is the potential diff. b/w two points. Two terminals are
necessary to measure a potential difference.
•Potential difference across two ends of wire conductor causes
drift of free electrons through the wire to produce electric
current.
•When the charge moves at the rate of 6.25 x 1018 electrons
flowing past a given point per second, the value of the current is
one ampere (A). I = Q/T.
•Types of electric charges for current.
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Magnetic Field Around an Electric current
•When any current flows, it has an associated magnetic field.
The magnetic field is in a plan perpendicular to the current.
The iron filling just a method of making the imaginary lines of
force visible.
•The fact that a wire conducting
current can become hot is evidence
of the fact that the work done by
the applied voltage in producing
current must be accomplished again
some form of opposition which
limit the amount of current that can be produced by the
applied voltage is called resistance .
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•Conductance: The opposite of resistance is conductance. The
lower the resistance, the higher the conductance.The symbol is
G. and the unit is the siemens (S).
•The Closed Circuit: Any electric circuit has three important
characteristics:
1. There must be a source of potential
difference.
2. There must be a complete path for
current flow.
3. The current path normally has
resistance.
•Electron Flow
•Conventional Current
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•Direct Current (DC)
•Alternating Current (AC)
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Source of Electricity
•Static Electricity by Friction
•Conversion of chemical Energy
•Electromagnetism
•Photo electricity
•Thermal Emission
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