1. Lecture 1: Intro & Circuit Variables Nilsson 1.1-1.6, 2.1-2.4 ENG17 : Circuits I Spring 2015 1 March 31, 2015

2. Overview Personal Introduction Course Introduction Units Circuit Analysis Voltage / Current Basic Circuit Element Power / Energy Voltage & Current Sources Electrical Resistance Circuit Model Kirchhoff’s Laws 2

3. Dr. Kyle Montgomery B.S. 2004 University of Houston 3 years @ Schlumberger M.S. 2008 Purdue University Ph.D. 2012 Purdue University –Thesis: Novel Approaches for Wide Bandgap Solar Cells 3

4. What I do now…besides teach… Advise students Research –Novel solar cells w/compound semiconductors –New materials for lighting, solar cells, and beyond –High speed, high power transistors –Alternative energy storage solutions 4

5. Philosophy…on teaching…and life Teaching is not confined to classroom time Conceptual understanding is key Life really sucks sometimes…how can I help? 5

6. Overview Personal Introduction Course Introduction Units Circuit Analysis Voltage / Current Basic Circuit Element Power / Energy Voltage & Current Sources Electrical Resistance Circuit Model Kirchhoff’s Laws 6

7. ENG17: Circuits 1 Electrical quantities and elements Resistive Circuits Transient and steady-state responses of RLC circuits Sinusoidal excitation and phasors Complex frequency and network functions Power Calculations 7

8. Course Structure TAs –Matt Clements –Songjie Bi –Chi Van Pham –Burcu Ercan –Yuhao Liu –Xin Zhao (Tuesday discussions) –Nathan Ellis (Thursday discussions) Course Website is: –http://www.kmontgomery.net/teaching/eng17/http://www.kmontgomery.net/teaching/eng17/ –Smartsite used primarily for grades Also using Piazza 8

9. Overview Personal Introduction Course Introduction Units Circuit Analysis Voltage / Current Basic Circuit Element Power / Energy Voltage & Current Sources Electrical Resistance Circuit Model Kirchhoff’s Laws 9

10. SI Units 10

11. Derived Units 11

12. Prefixes 12

13. Examples 13

14. Overview Personal Introduction Course Introduction Units Circuit Analysis Voltage / Current Basic Circuit Element Power / Energy Voltage & Current Sources Electrical Resistance Circuit Model Kirchhoff’s Laws 14

15. Big Picture Need justifies design Design specs filter to concept, circuit model, prototype Circuit analysis necessary for foundation 15

16. Overview Personal Introduction Course Introduction Units Circuit Analysis Voltage / Current Basic Circuit Element Power / Energy Voltage & Current Sources Electrical Resistance Circuit Model Kirchhoff’s Laws 16

17. Voltage 17

18. Current 18

19. Ohm’s Law 19

20. Water Analogy Water pressure = voltage Water flow = current 20

21. Overview Personal Introduction Course Introduction Units Circuit Analysis Voltage / Current Basic Circuit Element Power / Energy Voltage & Current Sources Electrical Resistance Circuit Model Kirchhoff’s Laws 21

22. Ideal Element 22 Passive sign convention

23. Fundamental Quantities 23 1.Voltage (v) 2.Current (i) 3.Charge (q) 4.Flux (Φ)

24. Overview Personal Introduction Course Introduction Units Circuit Analysis Voltage / Current Basic Circuit Element Power / Energy Voltage & Current Sources Electrical Resistance Circuit Model Kirchhoff’s Laws 24

25. Power ≠ Energy Power = Time Derivative of Energy UNITS! –Power in Watts –Energy in Watt-hrs or Joules Positive Power = Power Delivered to Circuit Negative Power = Power Extracted from Circuit 25

26. 26

27. Overview Personal Introduction Course Introduction Units Circuit Analysis Voltage / Current Basic Circuit Element Power / Energy Voltage & Current Sources Electrical Resistance Circuit Model Kirchhoff’s Laws 27

28. 5 Ideal Basic Circuit Elements Voltage Sources Current Sources Resistors Inductors Capacitors 28 “Active Elements” Generate Electric Energy “Passive Elements” Do NOT Generate Electric Energy

29. Ideal Sources 29 Voltage Source (const. voltage) Current Source (const. current) Circle means “Independent Source”

30. Dependent Sources 30 Voltage Sources Current Sources Diamond means “Dependent Source”

31. Schematics 31 Wire Assume No Resistance Node Any defined point (usually a point of intersection) Valid configuration

32. Schematics (w/dependents) 32 Valid configuration Invalid configuration Valid configuration

33. Schematics - GND Ground (GND) is a common connection Typically connect to Earth GND Always a zero [V] reference potential 33 GND Connect

34. Overview Personal Introduction Course Introduction Units Circuit Analysis Voltage / Current Basic Circuit Element Power / Energy Voltage & Current Sources Electrical Resistance Circuit Model Kirchhoff’s Laws 34

35. Ohm’s Law 35 Note change in sign Assume ideal resistance (no change w/time)

36. Conductance 36

37. Power & Ohm’s Law 37 Therefore… Ohm’s Law Power Relationship or

38. Examples 38

39. Overview Personal Introduction Course Introduction Units Circuit Analysis Voltage / Current Basic Circuit Element Power / Energy Voltage & Current Sources Electrical Resistance Circuit Model Kirchhoff’s Laws 39

40. Designing a Circuit Model 40

41. Additional Elements 41 Short Circuit Open Circuit Switch

42. Schematic 42 1.5V9V Batteries Lamp Case SwitchSpring

43. Overview Personal Introduction Course Introduction Units Circuit Analysis Voltage / Current Basic Circuit Element Power / Energy Voltage & Current Sources Electrical Resistance Circuit Model Kirchhoff’s Laws 43

44. The Setup 44 Use common subscripts Establish Reference Polarities Establish Nodes that Connect Elements 7 unknowns…need 7 equations From Ohm’s Law:

45. Kirchhoff’s Current Law (KCL) 45 The algebraic sum of all the currents at any node in a circuit equals zero. Therefore: Assign signs to currents at each node Positive (+) for current leaving a node Negative (-) for current entering a node Or vice versa

46. Kirchhoff’s Voltage Law (KVL) 46 The algebraic sum of all the voltages around any closed path in a circuit equals zero. Therefore: Assign signs to voltages in a loop Positive (+) for voltage rise Negative (-) for voltage drop Or vice versa

47. Observations 7 equations  4 equations –Because I and V are related through R, we only need one With only 2 branches at a node (in series), we only need to know 1 current 47

48. KCL Example 48

49. KVL Example 49