A short insight of electrical engineering.

1. BY:
ENGR. MOIN
AFZAL
National Skills University
Islamabad
MT-144 Basic Electrical &Electronics

2. Introduction!
 We see applications of electricity all around us.
 observance the presence of electricity in nature.
 Struggle of mankind has been able to put electricity for its use.
 All electronic and electrical products operate on electricity.
 e.g. computer system, cell phones, home entertainment system, lighting, heating,
and air-conditioning systems (all are applications of electricity).
 Further, its applications are limitless and beyond the imagination of mankind.

3. Cont…
 Clean form of energy and easy to transmit from one place to another place.
 All other forms of energy available in nature are, therefore, transformed into electrical
energy and then transmitted to places where electricity is to be used for doing some
work.
 Therefore, we can define electrical energy as a branch of study which deals with
generation, transmission, distribution, and utilization of electricity.

4. Cont…
 On the other hand, electronics engineering is an offshoot of electrical engineering.
 Deals with the theory and use of electronic devices in which electrons are
transported through vacuum, gas, or semiconductors.
 The motion of electrons in electronic devices like diodes, transistors, thyristors, etc.
are controlled by electric fields.
 Advances of electronics includes modern computers and digital communication
systems.
 Introduction of very large scale integrated (VLSI) circuits has led to the
miniaturization of all electronic systems.

5. Atomic Structure

6. Cont…
 All matter can be classified into either one of two groups:
1. Elements
2. Compounds
 In an element, all the atoms are the same. Examples of elements are aluminum,
copper, carbon, germanium, and silicon.
 A compound is a combination of elements.

7. Cont…
 Water, for example, is a compound consisting of the elements hydrogen and
oxygen.
 The smallest particle of any compound that retains the original characteristics of
that compound is called a molecule.
 OR
 A molecule is a group of two or more atoms formed when these atoms chemically
combine with each other. These atoms may either be same or of different
elements. For example, 2 atoms of hydrogen and one atom of oxygen combine to
form one molecule of water. Similarly, 2 atoms of hydrogen combine with each
other to form a molecule of hydrogen.

8. Cont…
 Atoms are composed of subatomic particles of electrons, protons, and neutrons in
various combinations.
 The electron is the fundamental negative charge (-) of electricity.
 Different kinds of theories have been represented by different scientists but here we
will discuss about some famous theories like:
 Dalton’s Theory
 Rutherford’s Theory
 Neil Bohr’s Theory

9. Cont…

10. Cont…

12. Electrons orbit the nucleus like planets orbits the sun

13. Bohr’s Model of the Atom:
 Electrons revolve about the nucleus or center of the atom in paths of concentric “shells,” or orbits.
 The proton is the fundamental positive (+) charge of electricity.
 Protons are found in the nucleus.
 The number of protons within the nucleus of any particular atom specifies the atomic number of that atom.
 For example, the silicon atom has 14 protons in its nucleus so the atomic number of silicon is 14.
 The neutron, which is the fundamental neutral charge of electricity, is also found in the nucleus.

17. Cont…
 Atoms of different elements differ from one another in the number of electrons and protons they contain.
 In its natural state, an atom of any element contains an equal number of electrons and protons.
 Since the negative (-) charge of each electron is equal in magnitude to the positive (+) charge of each proton,
the two opposite charges cancel. An atom in this condition is electrically neutral, or in balance.

18. Cont...

20. Cont…
 A stable (neutral) atom has a certain amount of energy, which is equal to the sum of the energies
of its electrons. Electrons, in turn, have different energies called energy levels.
 The energy level of an electron is proportional to its distance from the nucleus.
 Therefore, the energy levels of electrons in shells farther from the nucleus are higher than those
of electrons in shells nearer the nucleus.

21. Cont.…
 The electrons in the outermost shell are called valence electrons.
 When external energy such as heat, light, or electric energy is applied to certain
materials, the electrons gain energy. This may cause the electrons to move to a
higher energy level.
 An atom in which this has occurred is said to be in an excited state. An atom in an
excited state is unstable.

22. Cont…
 When an electron has moved to the outermost shell of its atom, it is least attracted by the positive charges of the
protons within the nucleus of its atom.
 If enough energy is then applied to the atom, some of the outermost shell or valence electrons will leave the
atom. These electrons are called free electrons.
 It is the movement of free electrons that provides electric current in a metal conductor.
 Each shell of an atom can contain only a certain maximum number of electrons. This number is called the quota
of a shell.

23. Cont…
 The orbiting electrons are in successive shells designated K,L, M, N, 0, P and Q at increasing distances
outward from the nucleus.
 Each shell has a maximum number of electrons for stability.
 After the K shell has been filled with 2 electrons, the L shell can take up to 8 electrons.
 The maximum number of electrons in the remaining shells can be 8, 18, or 32 for different elements.
 The maximum for an outermost shell, though, is always 8.

24. Energy Shells and the quota of electrons for
each shell

25. Electric Charge
 Electric Charge:
 In 1752, Benjamin Franklin flew a kite with a key attached to the string. As a thunderstorm
approached, the loose threads of the kite string began to stand up and repel one another, and
when Franklin brought his knuckle close to the key, he experienced a spark.
 Electric effects produced in this way are called static electricity.
 The concept of electric charge is the underlying principle for explaining all electrical
phenomena. Also, the most basic quantity in an electric circuit is the electric charge. We all
experience the effect of electric charge when we try to remove our wool sweater and have it
stick to our body or walk across a carpet and receive a shock.

26. Cont…
 Have you ever noticed the way that your hair is attracted to the comb when you comb your hair on a
dry day or the way that your hair stands on end after it is rubbed with a balloon.
 If so, you will recognize the attraction of the bits of paper to a plastic ruler shown in the adjacent figure.

27. Cont…
 If two neutral objects are rubbed together, each can become charged.
 For instance, when rubber and wool are rubbed together, electrons from atoms on
the wool are transferred to the rubber, as shown in the figure below.

28. Cont…
 Since some atoms can lose electrons and other atoms can gain electrons, it is
possible to cause a transfer of electrons from one object to another.
 When this takes place, the equal distribution of the positive and negative charges
in each object no longer exists.
 Therefore, one object will contain an excess number of electrons and its charge
must have a negative, or minus (-), electric polarity.

29. Cont…
 The other object will contain an excess number of protons and its charge must
have a positive, or plus (+), polarity.
 When a pair of objects contains the same charge, that is, both positive (+)or both
negative(-), the objects are said to have like charges.
 When a pair of bodies contains different charges, that is, one body is positive (+)
while the other body is negative (-), they are said to have unlike or opposite
charges.

30. Cont.…
 The law of electric charges may be stated as follows:
 “Like Charges repel each other; unlike charges attract each other.
 If a negative (-) charge is placed next to another negative (-) charge, the charges will
repel each other (shown in figure A)
 If a positive (+) charge is placed next to a negative (-) charge, they will be drawn
together (shown in figure C).

32. Cont…
 The Coulomb:
 Charge of an electron is very small. Coulomb (C) is the unit of charge.
 The charge of an electron is only 1.602 × 10-19 Coulomb (C).
 The magnitude of electric charge a body possesses is determined by the number of electrons
compared with the number of protons within the body. The symbol for the magnitude of the
electric charge is Q, expressed in units of coulombs (C). A charge of one negative coulomb, -Q,
means a body contains a charge of 6.25 x 10" more electrons than protons.

33. Cont.…
 What is the meaning of +Q?

34. Electric Field

35. Cont…

38. Magnetic Field:

39. Cont…