Node and Mesh Analysis
ELCT 220
Node and mesh
analysis
ELCT 220
1
Mesh analysis
The method of mesh currents
A circuit that can be drawn on a
plane surface with no branch
crossing another is a planar circuit
Method of mesh analysis applies
only to plana
Lesson 2 Resistors
Resistors:
devices used to limit current in a circuit
voltage drop V is proportional to current
I (Ideal resistor)
constant of proportionality is resistance
R
convert electrical energy (work) into
heat
Lesson 2 Resistors
USC ELCT 2
Power and Energy
ELCT 220
Lesson 3
Power and Energy
1
Power and energy
in a circuit element
Consider a circuit element, such as a
resistor:
Ir
Vr
Lesson 3
R
Vr is in volts [V]
Ir is in amps [A]
Power P = Vr Ir is in watts [W]
Power and Energy
2
Power and
Direct-Current
Generators and Motors
1
MOTORS AND GENERATORS
A motor is a machine that converts electric energy
into rotary mechanical energy.
Motors turn washing machines, dryers, fans,
furnace blowers, and much of the machinery
found in industry.
A g
Lesson 4 Batteries
ELCT 220
ELCT 220
Batteries
1
Introduction to batteries
Battery is a connected of
electrochemical cells (Galvanic cells or
Voltaic cells)
These cells are the sites of
electrochemical reactions that produce
a voltage between two termin
ELCT 220
Introduction to Electrical
Engineering
Lesson 1 Electrons
USC ELCT 220
1
Lesson 1 Electron Theory
Model of copper atom:
Copper is a good conductor
Bohr model shown below depicts 29
protons (and some neutrons) in the
nucleus, with 29 electrons in
Theorems
Some useful theorems
Principle of superposition
Examples
Thevenin and Norton theorems
Examples
Theorems
ELCT 220
1
Principle of superposition
A linear circuit that has more
than one source has a response
that is the sum of the responses
to each
Lesson 9
Magnetism
Laws, Units, Materials
Magnetics
1
Laws of Magnetism
Magnetic field is a force field, acting to apply a
force to conductors that carry currents
Amperes Law relates the magnetic field
intensity H to the current in a conductor setting
u
Wheatstone bridge circuit
Lesson 7
Fall 2012
Bridge circuit
1
Bridge circuit
S2
R1
Rx
VT
G
R3
S1
R2
Rx is an unknown resistance
R3 is a variable resistor with known values
G is a galvanometer (sensitive dc ammeter)
Fall 2012
Bridge circuit
2
Bridge circui
Two-wire and three-wire dc
power distribution circuits
Lesson 8
Two-wire distribution
Line drop calculation
Three lamps are connected to a 120 V
source
Each line resistance is 0.25 W
The lamps draw 1.5 A each
0.25 W
1.5 A
4.5 A 0.25 W
1.5 A
120 V
1.5
DC Permanent Magnet Motor Example: Motor runs at no load shaft speed of 110 rad/s when the rated
voltage of 48 V dc is applied to the armature terminals by a source. The no-load torque is small (just
enough to overcome friction) and is to be neglected. Ca