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Electronics Technology Fundamentals
Chapter 1
Principles of Electricity
1.0 The Oldest Analogy in Electronics
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© 2009 Pearson Higher Education,
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1.1 The Starting Point: Elements, Atoms and
Charge – P1

Matter



Matter – anything that has weight and occupies space
Element – substance that cannot be broken down into a
combination simpler substances
Atomic Structure


Atom – smallest particle of matter that retains the physical
characteristics of an element
Bohr Model



Simplest model of an atom
Central core (nucleus) – contains protons and neutrons
Electrons revolve around nucleus
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© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
1.1 The Starting Point: Elements, Atoms and
Charge – P2
Electronics Technology Fundamentals, 3rd ed.
Paynter and Boydell
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© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
1.1 The Starting Point: Elements, Atoms and
Charge – P3

Atomic Structure (Continued)




Atomic Number of an Atom – number of protons
Atoms contain an equal number of protons and
electrons
Electrons travel in orbital paths (shells)
Valence Shell



Outermost shell
Cannot hold more than eight electrons
Complete shell contains eight electrons
Electronics Technology Fundamentals, 3rd ed.
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© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
1.1 The Starting Point: Elements, Atoms and
Charge – P4
Electronics Technology Fundamentals, 3rd ed.
Paynter and Boydell
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© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
1.1 The Starting Point: Elements, Atoms and
Charge – P5

Charge



Force that causes two particles to be attracted to, or
repelled from, each other
Two types – positive and negative
Atom – proton (positive), electron (negative),
neutron (electrically neutral)
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© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
1.1 The Starting Point: Elements, Atoms and
Charge – P6


Attraction and Repulsion - Like charges repel each
other and opposite charges attract each other
Ions



Outside force can cause an electron to leave its orbit -atom
is referred to as a positive ion
Outside force can cause an atom to gain an electron -atom is
referred to as a negative ion
Free Electrons


An electron that is not bound to any particular atom
Can neutralize a positive ion
Electronics Technology Fundamentals, 3rd ed.
Paynter and Boydell
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© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
1.1 The Starting Point: Elements, Atoms and
Charge – P7
Electronics Technology Fundamentals, 3rd ed.
Paynter and Boydell
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© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
1.2 Current – P1

Current – the directed flow of charge through a
conductor


Thermal energy (heat) is sufficient to free electrons in
copper
Free electron motion is random unless outside force is
applied
Electronics Technology Fundamentals, 3rd ed.
Paynter and Boydell
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© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
1.2 Current – P2


Represented by the letter I (for intensity)
Measured in charge per unit time
Q
I
t
where
I = the intensity of the current
Q = the amount of charge
t = the time (in seconds) required for the
charge (Q) to pass
Electronics Technology Fundamentals, 3rd ed.
Paynter and Boydell
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© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
1.2 Current – P3



Coulomb (C) – represents the total charge of
approximately 6.25 x 1018 electrons
Unit of Current – 1 Ampere (A) = 1
coulomb/second (C/s)
Example:
3 coulombs of charge pass a point in a wire every
two seconds. Circuit current is found as
Q 3C
I 
 1.5 C/s  1.5 A
t 2s
Electronics Technology Fundamentals, 3rd ed.
Paynter and Boydell
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© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
1.2 Current – P4

Electron Flow Versus Conventional Current
Electronics Technology Fundamentals, 3rd ed.
Paynter and Boydell
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© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
1.2 Current – P5

Direct Current Versus Alternating Current


Direct Current (dc) – unidirectional, always flows
in one direction
Alternating Current (ac) – bidirectional,
periodically changes direction
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© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
1.2 Current – P6
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© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
1.3 Voltage – P1

Voltage – a “difference of potential” that generates a
directed flow of charge (current) through a circuit
Electronics Technology Fundamentals, 3rd ed.
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© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
1.3 Voltage – P2




Often referred to as electromotive force
(EMF)
Unit of Voltage – volt (V) = 1 joule/coulomb
Volt – the difference of potential that uses one
joule of energy to move one coulomb of charge.
1 V = 1 J/C
Electronics Technology Fundamentals, 3rd ed.
Paynter and Boydell
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© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
1.4 Resistance and Conductance – P1



Resistance – opposition to current
Unit of Resistance – ohm ( - Greek letter omega)
Ohm – the amount of resistance that limits current to
one ampere when one volt is applied
Electronics Technology Fundamentals, 3rd ed.
Paynter and Boydell
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© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
1.4 Resistance and Conductance – P2

Conductance – a measure of the ease which
current will pass through a component
1
G
R
where
G = conductance
R = resistance


Unit of Conductance – siemens (S)
Old Unit of Conductance – mhos (upside down
– omega symbol)
Electronics Technology Fundamentals, 3rd ed.
Paynter and Boydell
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© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
1.4 Resistance and Conductance – P3

Examples

Calculate the conductance of a 10 K resistor.
1
1
G 
 100 μS
R 10 kΩ

Calculate the resistance of a circuit that has a
conductance of 25 mS.
1
1
R 
 40 Ω
G 25 mS
Electronics Technology Fundamentals, 3rd ed.
Paynter and Boydell
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© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
1.5 Conductors, Insulators and Semiconductors
– P1

Conductors – materials that provide little
opposition to the flow of charge (current)



Example: copper
Few valence shell electrons, one valence shell
electron per atom makes the best conductor
Insulators – materials that normally block
current


Example: rubber
Complete valence shell (8 electrons)
Electronics Technology Fundamentals, 3rd ed.
Paynter and Boydell
21
© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
1.5 Conductors, Insulators and Semiconductors
– P2

Semiconductors – materials that are neither
good conductors nor good insulators


Examples: - graphite (used to make resistors)
- silicon
- germanium
Half-complete valence shells (four valence
electrons)
Electronics Technology Fundamentals, 3rd ed.
Paynter and Boydell
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© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
1.5 Conductors, Insulators and Semiconductors
– P3

Other Factors that Affect Resistance

Resistivity – the resistance of a specified volume of
an element or compound




CM-/ft – Circular-mil ohms per foot
-cm – Ohm-centimeters
Length
Cross-Sectional Area
Electronics Technology Fundamentals, 3rd ed.
Paynter and Boydell
23
© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
1.5 Conductors, Insulators and Semiconductors
– P4

Calculating the Resistance of a Conductor

R
A
where
 = resistivity (greek letter, rho)
ℓ = length
A = cross-sectional area
Electronics Technology Fundamentals, 3rd ed.
Paynter and Boydell
24
© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
1.5 Conductors, Insulators and
Semiconductors – P5

Example
Calculate the resistance of a 25 cm length of
copper that has a cross-sectional area of 0.04
cm2.

l
R    1.723 X 10 6 Ω  cm
A

 25cm 

2 
 0.04cm 
 1.08 X 10 3 Ω  1.08mΩ
Electronics Technology Fundamentals, 3rd ed.
Paynter and Boydell
25
© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.
1.5 Conductors, Insulators and Semiconductors
– P6

The Effects of Temperature on Resistance

Positive Temperature Coefficient



Resistance increases as temperature increases and vice
versa
Example: most conductors
Negative Temperature Coefficient


Resistance decreases as temperature increases and vice
versa
Example: most semiconductors and insulators
Electronics Technology Fundamentals, 3rd ed.
Paynter and Boydell
26
© 2009 Pearson Higher Education,
Upper Saddle River, NJ 07458. • All Rights Reserved.