Download Basic Electronics

National University of Computer & Emerging Sciences- CFD Campus
Department of Electrical Engineering
Basic Electronics
BS(CS) Fall 2014
Lecture_01
National University of Computer & Emerging Sciences
National University of Computer & Emerging Sciences- CFD Campus
Department of Electrical Engineering
Agenda Points
Lecture_01
1.
2.
3.
4.
Atoms and their structure
Charge
Potential Difference/ Voltage
Current
National University of Computer & Emerging Sciences
Electrons and Protons in the Atom
 Atom: An atom is the smallest particle of the basic elements
 Nucleus and Orbits: This atom consists of a central mass
called the nucleus and electrons outside.
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Structure of the Atom




Niels Bohr (1913):
Lord Rutherford (1871–1937)
Max Planck (1858–1947)
Albert Einstein (1879–1955)
 Atomic Number gives the number of protons or
electrons required in the atom for each element.
For the hydrogen atom, the atomic number is
one, which means that the nucleus has one
proton balanced by one orbital electron.
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Orbital Shells
 The planetary electrons are in successive shells called K, L, M, N, O, P,
and Q.
 Each orbital ring of electrons corresponds to a different energy level; the
larger the orbit, the higher the energy level of the orbiting electrons.
 For any specific shell, 2n2, Then the maximum number of electrons in;
For first shell is 2(1)2=2.
For the second shell 2(2)2=8,
For the third shell 2(3)2=18, and
For the fourth shell 2(4)2 =32.
 valence shell / valence electrons: The outermost shell of orbiting
electrons is called the valence shell, and the electrons in this shell are
called valence electrons
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Orbital Shells
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Elements, Molecules and Compounds

An Element :
It is defined as a substance that cannot be decomposed any further by
chemical action.

There are total 112 Elements (Periodic Table)

A Molecule:
A group of two or more atoms forms a molecule, e.g., (H2O).

A Compound:
It consists of two or more elements. The molecule is the smallest unit of a
compound with the same
chemical characteristics.
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Elements, Molecules and Compounds
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Conductors, Insulators, and Semiconductors
 When electrons can move easily from atom to atom in a
material, the material is a conductor. In general, all metals are
good conductors.
 A material with atoms in which the electrons tend to stay in
their own orbits is an insulator because it cannot conduct
electricity very easily. However, insulators can hold or store
electricity better than conductors. An Insulating material, such
as glass, plastic, rubber, paper, air, or mica, is also called a
dielectric, meaning it can store electric charge.
 A semiconductor is a material which has electrical
conductivity between that of a conductor such as copper and
that of an insulator such as glass. Semiconductors are the
foundation of modern electronics, including transistors, solar
cells, light-emitting diodes (LEDs), quantum dots and digital
and analog integrated circuits.
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National University of Computer & Emerging Sciences- CFD Campus
Department of Electrical Engineering
Charge
Charge:
Charge is the fundamental property of forms of matter that exhibit electrostatic
attraction or repulsion in the presence of other matter
Coulomb (C):
A practical unit called the coulomb (C) as equal to the charge of
electrons or protons stored in a dielectric.
National University of Computer & Emerging Sciences
Charge of an Electron
 Number of electrons in 1
Coulomb
 The charge of a single electron, designated Q e , is

 This value is the reciprocal of
electrons which
is the number of electrons in 1 coulomb of charge.
 Expressed mathematically,
 ( -Q e denotes that the charge of the electron is negative.)
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The Electric Field of a Static Charge
The ability of an electric charge to attract or repel another charge is a physical force.
All the lines form the electric field. The lines and the field are imaginary, since they cannot
be seen.
The force decreases inversely as the square of the distance. The larger the charge, the greater
the force. These relations describe Coulomb’s law of electrostatics.
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Coulomb’s law of electrostatics.
Electrons and Protons, they tend to be attracted to each other by the force of attraction between
opposite charges.
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Electric Charge, Electric Current, Electric
Potential (Voltage),

An electric charge must have either negative or
positive polarity, labelled +Q
or -Q , with
an excess of either electrons or protons.

A neutral condition is considered zero charge.
 Example:
A neutral dielectric has added to it 1.25 *1018
electrons. What is its charge in coulombs?
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National University of Computer & Emerging Sciences- CFD Campus
Department of Electrical Engineering
Voltage
Voltage:
The amount of potential energy between two points on a circuit. One point has more
charge than another. This difference in charge between the two points is called voltage.
Volt (V):
The potential difference between two points is one volt when one joule of energy is
expended in moving one coulomb of charge between those two points.
National University of Computer & Emerging Sciences
National University of Computer & Emerging Sciences- CFD Campus
Department of Electrical Engineering
Current
Current:
The charge in motion is an electric current.
Ampere (A):
The value of the current is one ampere (A) when one coulomb of charge per
second is moved.
Unit: Coulomb / sec = Ampere (A)
National University of Computer & Emerging Sciences
Electric Current:
 The flow of electric charges.
Electric Current
I=q
t
 Rate
 Andre Ampere (1775-1836)