Fundamentals of Electronics
 Student Information Sheet
 Syllabus
 Blackboard
 Books

Physics 110 Lab
 Labs start on Monday, September 12

I have all labs posted in the calendar

What Can I Expect?
 Lecture Style

PowerPoint, Chalkboard, Demos

Class participation is good.
 Exams

Exams problems are much like the homework problems and in-class exercises.

Where do we find electrical circuits?
 Communications

Radio, internet, telephone, television
 Data Processing

Desktop computers, servers
 Automobiles
 displays, sensors, motors
 Home
 lighting, heating, appliances
 Weather Stations
 wind speed, precipitation, temperature
 Power Plants
 moving magnets, transformers

 Scientific Notation
 Units of Measure

Scientific Notation and Prefixes
 1,000,000,000,000 10 12 – tera (T)
 1,000,000,000 10 9 – giga (G)
 1,000,000 10 6 – mega (M)
 1,000
 1
 0.001
 0.000001
10 3 – kilo (k) scientific notation and
10 0 for each.
10 -3 – milli (m)
10 -6 – micro ( m
)
 0.000000001
10 -9 – nano (n)
 0.000000000001
10 -12 – pico (p)

Electrical Units SI
Derived quantity power, radiant flux watt electric charge, quantity of electricity coulomb electric potential difference capacitance electric resistance volt farad ohm electric conductance magnetic flux magnetic flux density inductance
Celsius temperature siemens weber tesla henry degree
Celsius
Name
V
F
W
C
Symbol Expression in terms of other SI units
S
Wb
T
H
°C
J/s
-
W/A
C/V
V/A
A/V
V·s
Wb/m 2
Wb/A
-
Expression in terms of
SI base units m 2 ·kg·s -3 s·A m 2 ·kg·s -3 ·A -1 m -2 ·kg -1 ·s 4 ·A 2 m 2 ·kg·s -3 ·A -2 m -2 ·kg -1 ·s 3 ·A 2 m 2 ·kg·s -2 ·A -1 kg·s -2 ·A -1 m 2 ·kg·s -2 ·A -2
K

1.
Questions
What is the difference between AC, DC, and static electricity?
2.
3.
Why does a Van de Graaff Generator make your hair stand up?
(Give a technical answer.)
Why do clothes sometimes stick together after you take them out of the dryer?


From the Greek word “elektron” that means
“amber”
 There are two types of electricity:

Static Electricity - no motion of free charges

Current Electricity - motion of free charges
 Direct Current (DC)
 Alternating Current (AC)

2.2 Current
 Current is the rate of flow of charge through a conductor.

Conductor
 materials with free electrons
 e.g. copper, aluminum, gold, most metals
 Insulator
 materials with no free electrons
 e.g. glass, plastics, ceramics, wood

Semiconductor
 a class of materials whose electron conductivity is between that of a conductor and insulator
 Examples: Silicon, Germanium

Can Air be a Conductor?
 Yep!

Electrical Current
 Current - the rate of flow of charge through a conductor

Conventional Current
 Direction of flow of positive (+) charges

Electron Current
 Opposite to that of conventional current

Equation for Current
I=Q/t
I = the current in Amperes (A)
Q = the amount of charge in Coulombs (C) t = the time measured in seconds (s)
 The charge of an electron is 1.6 x 10 -19 C

Effect of Electric Currents on the Body
 0.001 A can be felt
 0.005 A is painful
 0.010 A causes involuntary muscle contractions
 0.015 A causes loss of muscle control
 0.070 A can be fatal if the current last for more than 1 second

Example Problem 2.0
 How much charge will pass through a conductor in 0.1 seconds if the current is
0.5 Amperes?
 How many electrons are required for this much charge?

Example 2.0
 T = 0.1 s I = 0.5 A
I = Q/t, so Q = I*t = (0.5 A)*(0.1 s) = 0.05 C
 Charge/e = 1.6 X 10 -19 C/e -
# Charges = 0.05 C/ 1.6 X 10 -19 C/e -
# Charges = 3.125 X 10 17 e -

Example 2.1
 Determine the current in amperes through a wire if 18.726 x 10 18 electrons pass through the conductor in 0.02 minutes.
 18.726 x 10 18 electrons, t = 0.02 min
Q = (18.726 x 10 18 e )(1.6 X 10 -19 C/e )
Q = 2.99616 C

3 C
 I = Q/t = 3 C/(0.02 min)(60 s/min)
 I = 2.4968

2.5 A

Example 2.2
 How long will it take 120 C of charge to pass through a conductor if the current is
2 A?
 I = Q/t, so t = Q/I = 120 C/2 A t = 60 s

Example Problem 2.3 and 2.4
 Write the following in the most convenient form using Table 2.1:
(a) 10,000 V
(b) 0.00001 A
(c) 0.004 seconds
(d) 520,000 Watts
(e) 0.0006 A
(f) 4200 V
(g) 1,200,000 V
(a) 10 4 V
(b) 10 -5 A
(c) 4 X 10 -3 s
(d) 5.2 X 10 5 W
(e) 0.6 mA
(f) 4.2 kV
(g) 1.2 MV
(h) 40 m
A
(h) 0.00004 A

Wire Gauge?
 AWG = American Wire Gauge
 AWG numbers indicate the size of the wire….but in reverse.
 For example, No. 12 gauge wire has a larger diameter than a No. 14 gauge wire.
 What do we use to keep wires from melting?

Answers: Fuses, Circuit Breakers, GFCI

Fuses

Circuit Breakers

GFCI = Ground Fault Current Interrupter
Used in kitchens and bathrooms
Trip quicker than circuit breakers

2.3 Voltage
 Voltage is the measure of the potential to move electrons.
 Sources of Voltage

Batteries (DC)

Wall Outlets (AC)
 The term ground refers to a zero voltage or earth potential.

Digital Multimeters (DMM)
Measurement
Voltage
Device Circuit Symbol
Current
Resistance
Ammeter
Ohmmeter
A

Batteries
 A battery is a type of voltage source that converts chemical energy into electrical energy
 The way cells are connected, and the type of cells, determines the voltage and capacity of a battery

More on Batteries
 Positive (+) and Negative (-) terminals
 Batteries use a chemical reaction to create voltage.
 Construction: Two different metals and Acid
 e.g. Copper, Zinc, and Citrus Acid
 e.g. Lead, Lead Oxide, Sulfuric Acid
 e.g. Nickel, Cadmium, Acid Paste

Batteries “add” when you connect them in series.
 Circuit Symbol:

 Equation for Voltage
V=W/Q
V = the voltage in volts (V)
Q = the amount of charge in Coulombs (C)
W = the energy expended in Joules (J)

Example Problem 2.7
 Determine the energy expended by a 12 V battery in moving 20 x 10 18 electrons between its terminals.

Example Problem 2.8
 (a) If 8 mJ of energy is expended moving
200 m
C from one point in an electrical circuit to another, what is the difference in potential between the two points?
 (b) How many electrons were involved in the motion of charge in part (a)?

2.4 Resistance and Ohm’s Law
 Resistance it the measure of a material’s ability to resist the flow of of electrons.
 It is measure in Ohms (
W
).

Ohm’s Law:
V = I R
V or E = voltage
I = current
R = resistance

Resistors

Example Problem 2.9
 Determine the voltage drop across a 2.2 k
W resistor if the current is 8 mA.
Example Problem 2.10
 Determine the current drawn by a toaster having an internal resistance of 22
W if the applied voltage is 120 V.

Example Problem 2.11
 Determine the internal resistance of an alarm clock that draws 20 mA at 120 V.

Equation for Resistance
R
 r

A r
= resistivity of the material from tables

= length of the material in feet (ft)
A = area in circular mils (CM) = area of a circle with a diameter of one mil (one thousandth of an inch)

Example Problem 2.12
 Determine the resistance of 100 yards of copper wire having an 1/8 inch diameter.
r for copper is 10.37 circular mils/ft (I know, sigh)
L = 100 yds = 300 ft
A
CM
= (d mils
) 2 = (125mils) 2 = 15,625
R = r ℓ /A = (10.37 CM/ft)(300 ft)/15625 CM
R = 0.199
W

Concept Questions
 How can you determine the current through a resistor if you know the voltage across it?

I = V/R
 How can you change the resistance of a resistor?

Change length, area, or temperature

Resistance depends on
Temperature
R
2

R
1

1
 a
1
( t
2
 t
1
)

R = resistances t = temperatures a
= temperature coefficient from tables

Example Problem 2.15
 The resistance of a copper conductor is 0.3
W at room temperature (20°C). Determine the resistance of the conductor at the boiling point of water (100°C).
 R
2
 R
2
 R
2
= R
1
[1 + a
1
(t
2
– t
1
)]
= (0.3
W)
[1 + 0.00393(100°-20°)]
= 0.394
W

Four-banded Resistor
Five-banded Resistor

Resistor Color Codes
0 Black
1 Brown
2 Red
3 Orange
4 Yellow
5 Green
6 Blue
7 Violet
8 Gray
9 White
5%
10%
Tolerance
Gold
Silver
Memorize this table.
Calculator

Example Problem 2.17

Determine the manufacturer’s guaranteed range of values for a carbon resistor with color bands of Blue, Gray, Black and Gold.

68 X 10 0

5% = 68
W 
3.4
W
Example Problem 2.18
 Determine the color coding for a
100 k
W resistor with a 10% tolerance.

100 k
W
= 100,000
W
 Band 1 (Brown) Band 2 (Black)
 Band 3 (Yellow) Band 4 (Silver)
0 Black
1 Brown
2 Red
3 Orange
4 Yellow
5 Green
6 Blue
7 Violet
8 Gray
9 White
Tolerance
5% Gold
10% Silver

Total Resistance for Resistors in Series
R
T

R
1

R
2
Total Resistance for Resistors in Parallel
R
1
T

1
R
1

1
R
2

Potentiometers
 They are three terminal devices with a knob.
 The knob moves a slider which changes the resistance between the terminals.
 Circuit Symbols:

What is the difference between E and V?
 E is the voltage supplied by a battery.
 V is the voltage measured across a resistor.

2.5 Power, Energy, Efficiency
 Power is the measure of the rate of energy conversion.
 Resistors convert electrical energy into heat energy.
 Equation for Power:
P = I E Power Delivered by a Battery
P = I V Power Dissipated by a Resistor
 What are some other ways that we can write this equation?

Power Equations
 P = IV but V = IR
 P = I(IR) = I 2 R from Ohm’s Law I = V/R
 P = (V/R)V = V 2 /R

Example Problem 2.19
 Determine the current drawn by a 180 W television set when connected to a 120 V outlet.
 P = 180 W

V = 120 V

I = P/V = 180 W/120 V = 1.5 A

Simple Circuit Problem
 Using circuit symbols, draw a circuit for a
9V battery connected to a 10
W resistor.
 Draw and label the direction of conventional current.
 Now include a voltmeter in your sketch that will measure the voltage drop across the resistors. What will it read?
 Include a ammeter that will measure the current through the resistor. What will it read?

Simple Circuit Problem
 How much power does the battery deliver?
 How much power does the resistor dissipate?

Example Problem 2.20
 Determine the resistance of a 1200W toaster that draws 10A.

 Energy and power are related:
W = P t
W = energy in Joules
P = power in Watts t = time in seconds

Example Problem 2.21
 Determine the cost of using the following appliances for the time indicated if the average cost is 9 cents/kWh.

(a) 1200W iron for 2 hours

(b) 160W color TV for 3 hours and 30 minutes

(c) Six 60W bulbs for 7 hours.

 Efficiency
 
P o 
100 %
P i
P i

P o

P l
1 hp

746 W

Example Problem 2.22
 Determine the efficiency of operation and power lost in a 5hp DC motor that draws
18A as 230V.

2.6 Series DC Networks
 Two elements are in series if they have only one terminal in common that is not connected to a third current carrying component.
 Total Resistance
R
T

R
1

R
2

R
3

...

R
N
 Current through a Series
E
I

R
T

 Consider Figure 2.32.
 E=24V, R
1
=2
W
, R
2
=4
W
, R
3
=6
W
 What is R
T
?
 What is I?
 What is V
1
, V
2 and V
3
?
 What is P
1
, P
2
, P
3
, and P
T
?

Kirchhoff’s Voltage Law

“The algebraic sum of the voltage rises and drops around a closed path must be equal to zero.”

V rises
 
V drops

0

 Voltage-divider rule
 “The voltage across any resistor in a series is some fraction of the battery voltage.”
V x

R x
E
R
T

2.7 Parallel DC Networks
 Two elements are in parallel if they have two terminals in common.
 Total Resistance
1

1
R
T
R
1

1
R
2
 Source Current
E
I

R
T

1
R
3

...

1
R
N

Concept Test
 For resistors in series, what is the same for every resistor? R, V or I?
 Answer: I
 For resistors in parallel, what is the same for every resistor? R, V or I?
 Answer: V

Kirchhoff’s Current Law

“The sum of the current entering a junction must equal to the current leaving.”

I ent ering
 
I leaving

Example Problem 2.28

Using Kirchhoff’s current law, determine the currents I
3
Figure 2.42
and I
6 for the system of
I
1
= I
2
+ I
3
I
3
+ I
4
= I
5
+ I
6
I
3
= I
1
- I
2
= 6 A – 2 A = 4 A
I
6
= I
3
+ I
4
- I
5
= 4 A + 6 A – 1 A = 9 A

 Consider Figure 2.35.
 E
1
=100V
 E
2
=50V




E
3
=20V
R
1
=10
W
R
2
=30
W
R
3
=40
W
 What is I?
 What is V
2
?

Example Problem 2.25
 Find V
1 and V
2 of Figure 2.36 using
Kirchhoff’s voltage law.

Voltage Sources in Series

 Current-divider rule
 “The current through any resistor in parallel with other resistors is some fraction of the source current.”
I x

IR
T
R x

Example Problem 2.26
 Determine the following for the parallel network in Fig. 2.40.

(a) R
T

(b) I

(c) I
2

(d) P
3

2.8 Series-Parallel Networks
Solve for R
T
, I, I
1
, I
2
, and V
1