Lecture 1
Fundamentals of Electricity
Hongwen Ren
@Dept.of Polymer-Nano Science and
Technology, Chonbuk National University
Room 703
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Why do we choose electronics?
1. We are living in the age of information technology
2. Electronics is at the very of foundation the information and
computer age
3. Sometimes it is unbelievable that we carry electronic
devices every day: digital watch, calculator, cell phone,
digital camera, notebook, MP3,…
4. Many different types of electronic equipment has invaded
our offices, homes, public places, such as TV, Air Condition,
Telephone, …
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Why Do we choose electronics?
5. It is almost close to “Magic” how even a child can switch a
channel, or increase/decrease the volume of sounds in a
TV at home by just clicking a few buttons without any
physical wiring and connection.
6. Electronics play more and more important role in our life.
We need to have some knowledge about electronics.
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Basic Concepts
1.
2.
3.
4.
5.
6.
7.
8.
Matter
Elements
Compounds
Atoms
Current
Voltage
Resistance
Summary
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Matter
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What is Matter?
Matter
Anything that occupies space and has weight ( or possesses
mass)
Solid- holds a particular shape and has definite volume.
(Any example?)
Liquid-doesn’t hold its own shape but it does occupy a
definite volume. (Any example?)
Gas- has no definite shape or volume. (Any example?)
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Matter May Be an Element
Element: The basic building block of nature. It is a substance
that can not be reduced to a simpler substance by chemical
means.
Examples of elements are gold, silver, copper, oxygen, carbon, …
Copper 구리
Aluminum 알루미늄
Carbon 탄소
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How Many Elements on Earth?
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Matter May be a Compound
Compound: The chemical combination of two or more
elements. A compound can be separated by chemical rather
than physical means.
Water is a Compound
Chemical means
Oxygen
Hydrogen
• Compounds are also pure substances..
• Water can be broken down into simpler substances –
hydrogen and oxygen
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Salt is a Compound
Na
Cl
Sodium + chlorine
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Molecule Vs Compound
A Molecule:
The smallest part of the compound that still retains the
properties of the compound. A molecule is the chemical
combination of two or more atoms.
Molecules of most elements are made up of only one of
atom of that element. Oxygen, along with nitrogen,
hydrogen, and chlorine are made up of two atoms.
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Atom and mixture
An Atom:
Is the smallest particle of an element that retains the
characteristic of the element
Mixture:
The physical combination of elements and compounds
examples: air (oxygen, carbon dioxide, and other gases).
Salt water(salt and water)
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Brief Summary: Matter & Atom
Element (gold, copper, hydrogen,
helium…)
Matter
Atom
Physical
combination
Mixture
Element 1
Molecule
(oxygen)
Atom
Element 2
…….
Chemical
combination
Molecule
(water)
Atom
Compound
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Check your understanding
Classify them: element, compound, molecule, or mixture
Milk, Helium, Sugar, Iron,
Salt, Ice, Hydrogen, air, hydrogen chloride
Carbon Dioxide, wood, Human body
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A Closer Look At Atoms
An atom is the smallest particle of an element.
Atoms of different elements differ from each other.
If there are over 100 known elements, then there
are over 100 known atoms.
For example:
Oxygen atom  Hydrogen atom  Nitrogen atom
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Structure of an Atom
Nucleus is located at the center of the atom; it contains protons
and Neutrons. The number of protons in the nucleus of the atom
is called the element’s atomic number
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Examples of Hydrogen and Helium Atoms
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Atom Mass
Each element has an atomic weight; the atomic weight is
the mass of the atom.
Atom mass: Atom = protons + neutrons + electrons
An electron’s mass is only
1/1845 that of Proton.
The mass of electrons is negligible.
Electron mass = 9.11 x 10-31 kg
Proton mass = 1.6726 x 10-27 kg
Neutron mass = 1.6749 x 10-27 kg
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Electrons orbiting around the nucleus
Shells are filled in sequence.
K is the first and then L, M,..
The maximum number of
electrons that can fill in
each shell
K=2, L=8, M=18, N=32
O=18, P=12, Q=2
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Shell Model of an Atom
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Definition of Valence Shell
The outer shell is the Valence Shell, the Number of electrons
it contains is the Valence
Copper
The outside electron can easily get rid of
the nucleus control when it gains energy
from external force, it becomes free electron
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Valence Shell: Electrons Gain or Lose
(1) The farther the valence shell is from the nucleus, the
less attraction the nucleus has on each valence electron.
(2) The greater the number of electrons in the valence shell
the less it conducts.
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Review After Class
1. In what forms can matter be found?
2. What is a substance called that cannot be reduced to a simpler
substance by Chemical means?
3. What is the smallest possible particle that retains the characteristic of
a compound ?
4. What is the smallest possible particle that retains the characteristic of
an element ?
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Review After Class
5. What atomic particle has a positive charge and a large
mass?
6. What atomic particle has no charge at all?
7. What atomic particle has a negative charge and a small
mass?
8. What does the number of electrons in the outermost
shell determine?
9. What is the term for describing the gaining or losing of
electrons
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Conductor, Insulator, Semiconductor
Materials that contain a large number of free electrons are
called Conductors (such as silver, copper, gold ..)
Material
Silver
Copper
Gold
Aluminum
Tungsten
Iton
Nichrome
Conductance
High
Low
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Conductor, Insulator, Semiconductor
Materials that can not provide free electrons or eliminating
free electrons are called insulators (Such as glass, paper,
rubber, oil, …)
Material
Mica
Glass
Teflon
Paper
Rubber
Bakelite
Oils
Procelain
Air
Insulation
properties
High
Low
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Conductor, Insulator, Semiconductor
Halfway between conductors and insulators are called
Semiconductor. Silicon and germanium are two
semiconductor materials
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Ionization
1. An atom that has the same number of electrons and protons
is said to be electrically balanced.
2. A balanced atom that receives electrons is
no longer balanced, it is said to be negatively
charged and is called negative ion.
3. A balance atom that loses electrons
is said to be a positive ion.
4. The process of gaining or losing
H-
A negatively charged
hydrogen ion
H+
electrons is called Ionization.
A positively charged
hydrogen ion
Current, Voltage, Resistance
With the external force, the movement of the electrons in one
direction is called current. Usually we use I to represent
current
Coulomb (C): 6.24x1018 electrons are added together and
the total charge is 1C
Ampere(A): 1 Coulomb of charge moves past a single
crossed-sectional surface in one second.
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Current, Voltage, Resistance
Electrons flow in a circuit because of the difference of potential
Battery can provide difference of potential, and the difference
of potential causes electrons to move or flow in a circuit.
The different of potential is called voltage (V).
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Current, Voltage, Resistance
Resistance: As the electrons move through the circuit, they
encounter atoms that do not really give up electrons.
This opposition to the flow of electrons is called resistance (R)
Conductors: Materials with a low resistance
Insulators: Materials with a high resistance
Resistance is measured in Ohms. The degree of
resistance of a material depends on its size, shape
and temperature
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Summary
1. Matter is anything that occupies space
2. Matter can be an element or compound
3. An element is the basic building block of nature
4. A compound is a chemical combination of two or more
elements
5. A molecule is the smallest unit of a compound that retains the
properties of the compound
6. An atom is the smallest unit of matter that retains the structure
of the element
7. An atom consists of a nucleus, which contains protons and
neutrons. It also has one or more electrons that orbit around
the nucleus.
8. Protons have a positive charge, electrons have a negative
charge, and neutrons have no charge
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Summary
9. The atomic number of an element is the number of protons
in the nucleus.
10. The atomic weight of an atom is the sum of protons and
neutrons.
11. The orbits of the electrons are called shells.
12. The outer shell of an atom is called the valence shell
13. The number of the electrons in the valence shell is called
the valence.
14. An atom that has the same number of protons as electrons
is electrically Balanced
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Summary
15. The process by which atoms gain or lose electrons is called
ionization
16. The flow of electrons is called current
17. Current is represented by the symbol I
18. The charge of 6,240,000,000,000,000,000 electrons is called
a coulomb.
19. An ampere of current is measured when one coulomb moves
past a given point in one second.
20. Ampere is represented by the symbol A
21. Current is measured in amperes.
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Summary
22. An electric current flows through a conductor when there
is an excess of Electrons at one end and a deficiency at
the other end.
23. A source that supplies excess electrons represents a
potential or electromotive force
24. The potential or electromotive force is referred to as
voltage.
25. Voltage is the force that moves electrons in a circuit.
26. The symbol E is used to represent voltage.
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Summary
27. A volt (V) is the unit for the measuring voltage
28. Resistance is the opposition to current flow.
29. Resistance is represented by the symbol R.
30. All materials offer some resistance to current flow.
31. The resistance of a material is dependent on the material’s
size, shape, and temperature.
32. Conductors are materials with low resistance
33. Insulators are materials with high resistance
34. Resistance is measured in ohms.
35. The Greek Letter  is used to represent ohms.
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Memorial Scientists
Coulomb
Ampere
Ohms ( )
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Self-Test
1. What criteria determines whether an atom is a good
conductor?
2. What determines whether a material is conductor,
semiconductor or insulator?
3. Why is it essential to understand the relationship between
conductors, semiconductors, and insulators
4. Explain the difference between current, voltage, and
resistance
5. Describe how the resistance of a material is determined.
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