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# Current vs. Voltage (I-V) Characteristic Notes | EduRev

## : Current vs. Voltage (I-V) Characteristic Notes | EduRev

``` Page 1

1
Lecture 4, Slide 1 EECS40, Fall 2003 Prof. King
Announcements
• Visit the class website to see updated TA
section assignments
http://www-inst.eecs.berkeley.edu/~ee40
• Lab section 13 (Mondays 6-9PM) is cancelled
• Prof. King’s Office Hour tomorrow (Thu. 9/4)
will be held from 8:30AM-9:30AM
• HW assignments will NOT be accepted in
class.  Turn in your assignments BEFORE
class on Friday in 240 Cory.
Lecture 4, Slide 2 EECS40, Fall 2003 Prof. King
Lecture #4
OUTLINE
• Circuit element I-V characteristics
• Construction of a circuit model
• Kirchhoff’s laws – a closer look
(Finish Chapter 2)
Page 2

1
Lecture 4, Slide 1 EECS40, Fall 2003 Prof. King
Announcements
• Visit the class website to see updated TA
section assignments
http://www-inst.eecs.berkeley.edu/~ee40
• Lab section 13 (Mondays 6-9PM) is cancelled
• Prof. King’s Office Hour tomorrow (Thu. 9/4)
will be held from 8:30AM-9:30AM
• HW assignments will NOT be accepted in
class.  Turn in your assignments BEFORE
class on Friday in 240 Cory.
Lecture 4, Slide 2 EECS40, Fall 2003 Prof. King
Lecture #4
OUTLINE
• Circuit element I-V characteristics
• Construction of a circuit model
• Kirchhoff’s laws – a closer look
(Finish Chapter 2)
2
Lecture 4, Slide 3 EECS40, Fall 2003 Prof. King
Current vs. Voltage (I-V) Characteristic
• Voltage sources, current sources, and
resistors can be described by plotting the
current (i) as a function of the voltage (v)
• Later, we will see that the I-V characteristic of
any circuit consisting only of sources and
resistors is a straight line.
+
v
_
i
Lecture 4, Slide 4 EECS40, Fall 2003 Prof. King
I-V Characteristic of Ideal Voltage Source
1. Plot the I-V characteristic for v
s
> 0.  For what
values of i does the source absorb power?  For
what values of i does the source release power?
2. Repeat (1) for v
s
< 0.
3. What is the I-V characteristic for an ideal wire?
+
_
v
s
i
i
+
v
_
v
Page 3

1
Lecture 4, Slide 1 EECS40, Fall 2003 Prof. King
Announcements
• Visit the class website to see updated TA
section assignments
http://www-inst.eecs.berkeley.edu/~ee40
• Lab section 13 (Mondays 6-9PM) is cancelled
• Prof. King’s Office Hour tomorrow (Thu. 9/4)
will be held from 8:30AM-9:30AM
• HW assignments will NOT be accepted in
class.  Turn in your assignments BEFORE
class on Friday in 240 Cory.
Lecture 4, Slide 2 EECS40, Fall 2003 Prof. King
Lecture #4
OUTLINE
• Circuit element I-V characteristics
• Construction of a circuit model
• Kirchhoff’s laws – a closer look
(Finish Chapter 2)
2
Lecture 4, Slide 3 EECS40, Fall 2003 Prof. King
Current vs. Voltage (I-V) Characteristic
• Voltage sources, current sources, and
resistors can be described by plotting the
current (i) as a function of the voltage (v)
• Later, we will see that the I-V characteristic of
any circuit consisting only of sources and
resistors is a straight line.
+
v
_
i
Lecture 4, Slide 4 EECS40, Fall 2003 Prof. King
I-V Characteristic of Ideal Voltage Source
1. Plot the I-V characteristic for v
s
> 0.  For what
values of i does the source absorb power?  For
what values of i does the source release power?
2. Repeat (1) for v
s
< 0.
3. What is the I-V characteristic for an ideal wire?
+
_
v
s
i
i
+
v
_
v
3
Lecture 4, Slide 5 EECS40, Fall 2003 Prof. King
I-V Characteristic of Ideal Current Source
1. Plot the I-V characteristic for i
s
> 0.  For what values
of v does the source absorb power?  For what
values of v does the source release power?
2. Repeat (1) for i
s
< 0.
3. What is the I-V characteristic for an open circuit?
i
i
+
v
_
v
i
s
Lecture 4, Slide 6 EECS40, Fall 2003 Prof. King
I-V Characteristic of Ideal Resistor
1. Plot the I-V characteristic for R = 1 k? .  What is the
slope?
i
i
+
v
_
v
R
Page 4

1
Lecture 4, Slide 1 EECS40, Fall 2003 Prof. King
Announcements
• Visit the class website to see updated TA
section assignments
http://www-inst.eecs.berkeley.edu/~ee40
• Lab section 13 (Mondays 6-9PM) is cancelled
• Prof. King’s Office Hour tomorrow (Thu. 9/4)
will be held from 8:30AM-9:30AM
• HW assignments will NOT be accepted in
class.  Turn in your assignments BEFORE
class on Friday in 240 Cory.
Lecture 4, Slide 2 EECS40, Fall 2003 Prof. King
Lecture #4
OUTLINE
• Circuit element I-V characteristics
• Construction of a circuit model
• Kirchhoff’s laws – a closer look
(Finish Chapter 2)
2
Lecture 4, Slide 3 EECS40, Fall 2003 Prof. King
Current vs. Voltage (I-V) Characteristic
• Voltage sources, current sources, and
resistors can be described by plotting the
current (i) as a function of the voltage (v)
• Later, we will see that the I-V characteristic of
any circuit consisting only of sources and
resistors is a straight line.
+
v
_
i
Lecture 4, Slide 4 EECS40, Fall 2003 Prof. King
I-V Characteristic of Ideal Voltage Source
1. Plot the I-V characteristic for v
s
> 0.  For what
values of i does the source absorb power?  For
what values of i does the source release power?
2. Repeat (1) for v
s
< 0.
3. What is the I-V characteristic for an ideal wire?
+
_
v
s
i
i
+
v
_
v
3
Lecture 4, Slide 5 EECS40, Fall 2003 Prof. King
I-V Characteristic of Ideal Current Source
1. Plot the I-V characteristic for i
s
> 0.  For what values
of v does the source absorb power?  For what
values of v does the source release power?
2. Repeat (1) for i
s
< 0.
3. What is the I-V characteristic for an open circuit?
i
i
+
v
_
v
i
s
Lecture 4, Slide 6 EECS40, Fall 2003 Prof. King
I-V Characteristic of Ideal Resistor
1. Plot the I-V characteristic for R = 1 k? .  What is the
slope?
i
i
+
v
_
v
R
4
Lecture 4, Slide 7 EECS40, Fall 2003 Prof. King
“Lumped Element” Circuit Modeling
(Model = representation of a real system which simplifies analysis)
• In circuit analysis, important characteristics are
grouped together in “lumps” (separate circuit
elements) connected by perfect conductors (“wires”)
• An electrical system can be modeled by an electric
circuit (combination of paths, each containing 1 or
more circuit elements) if
? = c/f >> physical dimensions of system
Distance travelled by a particle travelling at the speed of light
in one period
Example:  f = 60 Hz
? = 3 x 10
8
m/s / 60 = 5 x 10
6
m
Lecture 4, Slide 8 EECS40, Fall 2003 Prof. King
Construction of a Circuit Model
• The electrical behavior of each physical
component is of primary interest.
• We need to account for undesired as well
as desired electrical effects.
• Simplifying assumptions should be made
wherever reasonable.
Page 5

1
Lecture 4, Slide 1 EECS40, Fall 2003 Prof. King
Announcements
• Visit the class website to see updated TA
section assignments
http://www-inst.eecs.berkeley.edu/~ee40
• Lab section 13 (Mondays 6-9PM) is cancelled
• Prof. King’s Office Hour tomorrow (Thu. 9/4)
will be held from 8:30AM-9:30AM
• HW assignments will NOT be accepted in
class.  Turn in your assignments BEFORE
class on Friday in 240 Cory.
Lecture 4, Slide 2 EECS40, Fall 2003 Prof. King
Lecture #4
OUTLINE
• Circuit element I-V characteristics
• Construction of a circuit model
• Kirchhoff’s laws – a closer look
(Finish Chapter 2)
2
Lecture 4, Slide 3 EECS40, Fall 2003 Prof. King
Current vs. Voltage (I-V) Characteristic
• Voltage sources, current sources, and
resistors can be described by plotting the
current (i) as a function of the voltage (v)
• Later, we will see that the I-V characteristic of
any circuit consisting only of sources and
resistors is a straight line.
+
v
_
i
Lecture 4, Slide 4 EECS40, Fall 2003 Prof. King
I-V Characteristic of Ideal Voltage Source
1. Plot the I-V characteristic for v
s
> 0.  For what
values of i does the source absorb power?  For
what values of i does the source release power?
2. Repeat (1) for v
s
< 0.
3. What is the I-V characteristic for an ideal wire?
+
_
v
s
i
i
+
v
_
v
3
Lecture 4, Slide 5 EECS40, Fall 2003 Prof. King
I-V Characteristic of Ideal Current Source
1. Plot the I-V characteristic for i
s
> 0.  For what values
of v does the source absorb power?  For what
values of v does the source release power?
2. Repeat (1) for i
s
< 0.
3. What is the I-V characteristic for an open circuit?
i
i
+
v
_
v
i
s
Lecture 4, Slide 6 EECS40, Fall 2003 Prof. King
I-V Characteristic of Ideal Resistor
1. Plot the I-V characteristic for R = 1 k? .  What is the
slope?
i
i
+
v
_
v
R
4
Lecture 4, Slide 7 EECS40, Fall 2003 Prof. King
“Lumped Element” Circuit Modeling
(Model = representation of a real system which simplifies analysis)
• In circuit analysis, important characteristics are
grouped together in “lumps” (separate circuit
elements) connected by perfect conductors (“wires”)
• An electrical system can be modeled by an electric
circuit (combination of paths, each containing 1 or
more circuit elements) if
? = c/f >> physical dimensions of system
Distance travelled by a particle travelling at the speed of light
in one period
Example:  f = 60 Hz
? = 3 x 10
8
m/s / 60 = 5 x 10
6
m
Lecture 4, Slide 8 EECS40, Fall 2003 Prof. King
Construction of a Circuit Model
• The electrical behavior of each physical
component is of primary interest.
• We need to account for undesired as well
as desired electrical effects.
• Simplifying assumptions should be made
wherever reasonable.
5
Lecture 4, Slide 9 EECS40, Fall 2003 Prof. King
Terminology: Nodes and Branches
Node: A point where two or more circuit elements
are connected – entire wire
Branch: A path that connects two nodes
Lecture 4, Slide 10 EECS40, Fall 2003 Prof. King
Notation: Node and Branch Voltages
• Use one node as the reference (the “common”
or “ground” node) – label it with a symbol
• The voltage drop from node x to the reference
node is called the node voltage v
x
.
• The voltage across a circuit element is defined
as the difference between the node voltages at
its terminals
Example:
+
_
v
s
+
v
a
_
+
v
b
_
ab
c
R
1
R
2
–v
1
+
```
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