Introduction to circuit elements used in linear circuit analysis

1. CIRCUIT ELEMENTS
Chapter 2

2. OVERVIEW
• Five ideal basic circuit elements
• voltage sources
• current sources
• resistors
• inductors
• capacitors

3. VOLTAGE & CURRENT SOURCES
• Electrical Source is a device capable of converFng nonelectric energy into electric
energy
• baHery ‐ chemical to electrical
• dynamo* ‐ mechanical to electrical (generator) or electrical to mechanical (motor)
dynamo
http://commons.wikimedia.org/wiki/File:Hjorth_dynamo_1855.JPG
Note: we want to determine whether the sources are delivering or absorbing power.
This is most important for analysis.

4. VOLTAGE & CURRENT SOURCES
• Ideal Voltage Source is a circuit element that maintains a prescribed voltage
across its terminal regardless of the current flowing in those terminals.
• Ideal Current Source is a circuit element that maintains a prescribed current
through its terminals regardless of the voltage across its terminals
• truly independent
• not affected by environment or external forces
• do not exist in a pracFcal sense

5. VOLTAGE & CURRENT SOURCES
• Using ideal sources forces us to make a tradeoff between analyFcal simplicity and the
pracFcality of relaFng voltage and current in our source.
Dependency adds a complexity to our circuit analysis but it provides a more realis=c
model of behavior.
• Ideal sources can be further delineated by dependency (i.e. independent vs.
dependent voltage or current source)

6. VOLTAGE & CURRENT
SOURCES
• Circuit symbols for ideal voltage source
showing magnitude and polarity and ideal
current source showing magnitude and its
reference direcFon
• Note that the symbols are circular

7. VOLTAGE & CURRENT
SOURCES
• Dependent sources require
controlling voltage or current,
equaFon to compute the supplied
voltage or current from the
controlling value, and the
reference polarity for voltage and
reference direcFon for current.
• Dependent sources are
represented by diamonds.

8. VOLTAGE & CURRENT
SOURCES
voltage-controlled dependent voltage source

9. VOLTAGE & CURRENT
SOURCES
voltage-controlled dependent voltage source
voltage-controlled dependent current source

10. VOLTAGE & CURRENT
SOURCES
voltage-controlled dependent voltage source
voltage-controlled dependent current source
current-controlled dependent voltage source

11. VOLTAGE & CURRENT
SOURCES
voltage-controlled dependent voltage source
voltage-controlled dependent current source
current-controlled dependent voltage source
current-controlled dependent current source

12. VOLTAGE & CURRENT
SOURCES
voltage-controlled dependent voltage source
voltage-controlled dependent current source
current-controlled dependent voltage source
current-controlled dependent current source
α has the dimension amperes per volt and
has the dimension volts per ampere.

13. ONE MORE THING...
• Ac5ve Element models a device capable of genera=ng electric energy.
• ideal sources
• Passive Element models a device capable of absorbing electric energy.
• resistors, inductors, capacitors