Transcript Lecture 1 - University of Minnesota Duluth

ECE 2006
CIRCUIT ANALYSIS
University of Minnesota - Duluth
Lecture 1
Instructor:
Scott R.Norr, PE
• BSEE – North Dakota State University – 1986
• Registered Professional Engineer, MN –1994
• Minnesota Power – 1986 to 1997
• ECE Dept. at UM – Duluth - 1999 to Present
Course Details:
• Textbook: Alexander/Sadiku, Fundamentals of
Electric Cricuits, 4th Ed.
• Lab Place/Time: Tuesdays – MWAH 391
• Course Assessment:
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Homework: 10%
Labs: 25%
Midterms: 40%
Final: 25%
TOPICS
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Fundamental Laws of Electricity
Circuit Theory
Analysis Methods
Operational Amplifiers
Energy Storage in Caps and Inductors
Transient Circuits
AC Circuits
A Crude History of Electricity
• 600 BC: Ancient Greeks rub amber on cat fur to
produce static charge
• Circa 0 AD: Persians in present-day Iraq
invent the battery for unknown
(probably medical) purposes
• 1720’s:
Stephen Gray shows that static charges
can be ‘conducted’ from point to point
History (Cont.)
• 1750’s: Benjamin Franklin’s One Fluid Theory
of Electricity unifies scientific approaches to
electricity and forms the foundation of modern
electrical theory
• 1800’s: Alessandro Volta makes his Voltaic Pile
using zinc and copper disks submersed in an
electrolytic solution (acid), thus re-inventing the
battery, 1800 years after the Persians
History (Cont.)
• 1820’s: Hans Oerstad discovers electromagnetism
with his famous “compass and currentcarrying wire” experiments
– Andre-Marie Ampere defines electric current
and electromagnetism, invents the ammeter
– Georg Ohm delivers his theory of electricity,
including what later became Ohm’s Law
• 1830’s: Michael Faraday enters the game
and things get intense
Physics of Electricity
• Charge (q) – fundamental property of
atomic structures; measured in Coulombs
– One electron has a charge of -1.602 x10-19 C
• Electric Current (i) – measures the rate of
change in Charge; unit is Amperes (C/s)
– Relationship:
i = dq/dt
Physics - Continued
• Voltage (v) – The Electromotive Force (emf)
required to move Charge around a circuit.
Indicative of the Electric Field. Also called
Potential Difference; measured in Volts (J/C or
N-m/C)
– Relationship to charge:
v = dw/dq
Physics – Continued Some More
• Power (p) – Rate of change in work (the
expending of energy in time); measured in
Watts (J/s)
p = dw/dt = dw/dq * dq/dt = vi
Electric Conventions:
• Current Convention:
Electric Conventions (Cont.)
• Voltage Rise/Drop Convention
Electric Conventions (Cont.)
• Source/Load Convention
Fundamental Laws
• Ohm’s Law: V = I*R
• Kirchoff’s Laws:
– Voltage: Sum the voltages around a loop to
Zero
– Current: Sum the currents around a node to
Zero
• Power Equation: P = V*I
Maximum Power Transfer
• Power Transfer is maximized when load
impedance equals source impedance
Laboratory Equipment
• Oscilloscope
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1 M-Ohm Impedance
“Shunt” Device
Measures Voltages
Always measure voltages with respect to scope
ground
Laboratory Equipment (Cont.)
• Multimeter
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Measures Voltage, Current, Resistance, etc.
“Shunt” Device for Voltage (High Impedance)
“Series” Device for Current (Low Impedance)
Acts as a DC source when measuring
Resistance
– NEVER measure resistance on an Energized
Circuit
SAFETY
• CONTACT WITH ELECTRIC
CURRENT CAN CAUSE DEATH
• As little as 100 milliamperes (0.1 Amp) of
electric current can kill, if it travels
across the heart
SAFETY (Cont.)
• Follow Instructions, Ask for Clarification
• Know where Safety Equipment is
Located - Fire Extinguishers, Telephones, Fire
Blankets, Eye Wash Stations, etc.
• Always Assume an Electric Circuit is Hot
(Energized) and Dangerous and Act
Accordingly
SAFETY (Cont.)
• Keep Work Areas Clean and Uncluttered
• Double Check Circuit Wiring before
Energizing
• Never Work Alone
• Wire with One Hand - Minimizes exposure to
the Heart
SAFETY CONCLUSIONS
Always understand the Laboratory
Procedures before touching anything.
Always assume that electric circuits are
potentially live and dangerous.
Make sure there are adequate life saving
resources available and know how to use
them.
Resistor Color Code
Blk BR Red Or Yel Gr Blu Vi Gry Wht
0 1
2 3 4 5 6 7 8
First Band – “Tens” Column
Second Band – “Ones” Column
Third Band – Power of 10
Fourth Band – Tolerance:
Gold = 5% , Silver = 10%
Fifth Band – Ignore for now
In this example: 10 x 102 =1000 Ohms +/- 5%
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