EE_10_F07_Lecture 2

# EE_10_F07_Lecture 2 - UCLA ELECTRICAL ENGINEERING...

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UCLA E LECTRICAL E NGINEERING D EPARTMENT : EE 10: C IRCUIT A NALYSIS 1 L ECTURE 2 EE 10: CIRCUIT ANALYSIS LECTURE NOTES: OCTOBER 3, 2005 OUTLINE REVIEW ........................................................................................................................................ 2 INDEPENDENT VOLTAGE AND CURRENT SOURCES ..................................................... 3 Background ............................................................................................................................. 3 Voltage and Current Sources .................................................................................................. 3 Independent and Dependent Sources ...................................................................................... 3 Care in Identifying Possible Invalid Circuit Configurations .................................................. 3 ELECTRICAL RESISTANCE .................................................................................................... 5 Resistance and Resistivity ........................................................................................................ 5 Ohm’s Law .............................................................................................................................. 5 RESISTOR SYMBOLS ................................................................................................................ 7 CONDUCTANCE ......................................................................................................................... 7 TYPICAL RESISTANCE VALUES ........................................................................................... 7 POWER DISSIPATION IN RESISTORS .................................................................................. 8 DEVELOPMENT OF CIRCUIT MODELS ............................................................................... 9 Electric Power Transmission Line Example ........................................................................... 9 THE TERMS: OPEN AND SHORT CIRCUIT ....................................................................... 11 FUNDAMENTAL CIRCUIT LAWS: KIRCHHOFF’S LAWS ............................................. 12 KIRCHOFF’S CURRENT LAW ............................................................................................... 12 NEW Definition: Circuit Node .............................................................................................. 12 KIRCHHOFF’S VOLTAGE LAW ........................................................................................... 16 NEW Definition: Closed Circuit Path ................................................................................... 16 EXAMPLE VALID AND INVALID PATHS ........................................................................... 19 EXAMPLE SOLUTION TO A CIRCUIT PROBLEM USING KIRCHHOFF’S LAWS ... 21 REVIEW ...................................................................................................................................... 24 1

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UCLA E LECTRICAL E NGINEERING D EPARTMENT : EE 10: C IRCUIT A NALYSIS 1 L ECTURE 2 REVIEW Areas to focus on for core knowledge and skills are areas highlighted in review sections of lectures and the homework. 1. Circuit Models 2. Problem Solving 3. Charge 4. Current 5. Voltage 6. Passive Sign Convention: Study and Understand Ask Questions 7. Power 8. Power Transfer Polarity Questions? 2
UCLA E LECTRICAL E NGINEERING D EPARTMENT : EE 10: C IRCUIT A NALYSIS 1 L ECTURE 2 INDEPENDENT VOLTAGE AND CURRENT SOURCES BACKGROUND Both simple and complex circuit systems rely on stable voltage and current sources to establish stable signals. Stable voltage and current sources enable: Stable “clock” oscillators for stable time references Stable analog signal processing for telecommunications, measurement, and consumer electronics systems. Stable control systems for automotive and aerospace vehicle systems. Ideal voltage and current sources maintain a fixed voltage or current, independent of the presence of external circuit elements that may draw very large power from the ideal source. VOLTAGE AND CURRENT SOURCES Ideal Voltage Source: A two-terminal Voltage Source that establishes a constant voltage across its terminals for all values of current flowing into or out of its terminals. Ideal Current Source: A two-terminal Current Source that establishes a constant current through its terminal pair for any value of voltage across its terminals. INDEPENDENT AND DEPENDENT SOURCES Voltage and Current Sources may be Independent or Dependent Sources. Independent sources operate with constant outputs under all conditions. Dependent sources provide an output current or voltage that is proportional to a current or voltage sampled elsewhere in the circuit. The dependent source is controlled by another signal. CARE IN IDENTIFYING POSSIBLE INVALID CIRCUIT CONFIGURATIONS Ideal Voltage or Current sources may be included in circuit designs in a configuration that leads to a mathematically invalid result.

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