1. Light bulb When switch is closed, bulbs are … Brighter The same Dimmer than the bulb above (?)

2. When switch is closed, the right bulb will be … Brighter The same Dimmer than the left bulb now (?)

3. EXAMPLE: What’s the voltage across, and the current thru each resistor? 12V 100  200  (compare with equivalent R method …)

4. EXAMPLE: What’s the voltage across, and the current thru each resistor?

5. Electric circuits: Kirchhoff’s Rules start

6. Electric circuits: Kirchhoff’s Rules start

7. Electric circuits: Kirchhoff’s Rules start

8. Electric circuits: Kirchhoff’s Rules start

9. Electric circuits: Kirchhoff’s Rules start

10. The height analogy

17. (weeeee!)

18. The height analogy

28. Electric circuits: Kirchhoff’s Rules Rule 1: The sum of voltage drops around a loop is always zero! (Energy conserved)

29. The voltage divider 1/2 (solve for I ) No numbers yet!

30. The voltage divider 2/2 (solve for V 1 & V 2 ) No numbers yet!

31. The voltage divider: Numbers!

32. Electric circuits: Kirchhoff’s Rules Rule 2: The sum of currents entering a junction must equal the sum of currents leaving it! (comes in = goes out)

33. Parallel Circuit No numbers yet!

34. Parallel Circuit Numbers

35. A not-to-bad example: 19.27 + + NY Kirchhoff’s laws step-by-step …

36. A not-to-bad example: 19.27 + + Currents! 1)Guess directions

37. A not-to-bad example: 19.27 + + Currents! 1)Guess directions 2)Use nodes to reduce set

38. A not-to-bad example: 19.27 Voltage Loops! Loop 1 + + ab cd + - -

39. A not-to-bad example: 19.27 Voltage Loops! + + ab c d + - - - Loop 2

40. Solve the equations for the currents! No problem here

41. A not-to-bad example: 19.27 The Check! + + + + - - - -

42. A bad example: + +

43. I ) Assign currents! + +

44. + +

45. + +

46. II ) Look at currents in & out of nodes + +

47. + +

48. III ) Assign voltage differences (drops) + - + + + - - - + -

49. IV ) Loops! Voltage differences must add to zero + - + + + - - - + - a bc d

50. + - + + + - - - + - a bc d

51. V ) Now, solve those currents More space

54. Now …

55. + - + + + - - + -

56. + - + + + - - + -