E E 1205 Circuit Analysis

1. E E 1205 Circuit Analysis Lecture 1 - Introduction to Electrical Engineering

2. Overview of Electrical Engineering • Electrical engineers design systems with two main objectives: to… • Gather, store, process, transport or present information • Distribute, and convert energy between different forms • Electrical systems can be divided into seven major classifications.

3. 7 Linked Classifications of Electrical Systems • Communications Systems • Computer Systems • Control Systems • Electromagnetics • Electronics • Power Systems • Signal Processing Systems

4. Communications Systems • Telephony • Analog and Digital • Switched Channels • Radio • Broadcast AM, FM, & SW • Two-Way • Television

5. Computer Systems • Programmable Microcircuits • High-speed switching of logic circuits • Used for • Computation • Control

6. Control Systems • Automated • Adaptable • Faster Operation than Manual • More Reliable than Manual • Modern high-performance aircraft rely on automated control systems

7. Electromagnetics • Antennas for Sending & Receiving Information • Cell Phones • Satellite Dishes • Magnetrons for generation of Microwave Energy • Induction Heating for Industrial processes

8. Electronics • Material Properties • Devices • Circuits • Used for Detecting, Amplifying and Switching Electrical Signals

9. Power Systems • Large networks connected by low frequency a-c transmission lines • Small networks in aircraft and spacecraft • Electromechanical Energy Conversion • Power Electronics • High frequency switching converters • High efficiency, high power density

10. Signal Processing Systems • Transform and manipulate signals and the information they contain • Image processing • Data from weather satellites • MRI scans of the human body • Noise reduction • Encryption

11. Circuit Theory • Mathematical modeling of physical phenomena • Circuit theory is a special case of electromagnetic field theory • General EM theory is more complex than circuit theory • General EM theory requires more complex mathematics

12. Three Basic Assumptions of Circuit Theory • Electric effects happen instantaneously throughout a system • Net Charge on every component in the system is zero • No magnetic coupling between components

13. Effect of Frequency

14. Problem Solving • Identify what is given and what is to be found. • Sketch a circuit diagram or other visual model • Think of several solution methods and a way of choosing between them • Calculate a solution

15. Problem Solving (continued) • Use your creativity • If your efforts are not converging to a solution, you may want to rethink your assumptions. • Test your solution • Is your answer reasonable? • Does your answer validate your assumptions?

16. International System of Units • Frequency hertz (Hz) s-1 • Force newton (N) kg·m/s2 • Energy or work joule (J) N·m • Power watt (W) J/s • Electric charge coulomb A·s • Electric potential volt (V) W/A • Electric resistance ohm () V/A • Electric conductance siemens (S) A/V

17. International System of Units (continued) • Electric capacitance farad (F) C/V • Magnetic flux weber (Wb) V·s • Inductance henry (H) Wb/A

18. Standardized Prefixes • atto a 10-18 • femto f 10-15 • pico p 10-12 • nano n 10-9 • micro  10-6 • milli m 10-3 • centi c 10-2 • deci d 10-1 • deka da 10 • hecto h 102 • kilo k 103 • mega M 106 • giga G 109 • tera T 1012 • peta P 1015 • exa E 1018

19. Circuit Analysis: An Overview • A circuit model is used to connect our visualization to our analysis of a physical system • The elements of our circuit model are ideal circuit components. • The behavior of output parameters is governed by physical/mathematical laws for the elements of the circuit model.

20. Voltage and Current • Voltage is the energy per unit of charge. • Current is the rate of flow of charge.

21. Voltage and Current (continued) • The relationship between voltage and current in a circuit element defines that circuit element. • Both voltage and current have associated polarities. • These polarities determine the direction of power flow.

22. Ideal Basic Circuit Element • Three attributes of an ideal circuit element: • There are only two terminals • Described mathematically in terms of current and/or voltage • Cannot be subdivided into smaller components

23. Voltage Polarity Definitions • Positive v • voltage drop from 1 to 2 or • voltage rise from 2 to 1 • Negative v • voltage drop from 2 to 1 or • voltage rise from 1 to 2

24. Current Polarity Definitions • Positive i • Positive charge flowing from 1 to 2 • Negative charge flowing from 2 to 1 • Negative i • Positive charge flowing from 2 to 1 • negative charge flowing from 1 to 2

25. Passive Sign Convention • Whenever the reference direction for the current in an element is in the direction of the reference voltage drop, use a positive sign in any expression that relates voltage to current. Otherwise, use a negative sign.

26. Power and Energy • Power associated with a circuit element is consumed by that circuit element when the value of power is positive. • Conversely, power is generated, or produced by the element if the value consumed is negative.

27. Expression of Power