1. Unit 12Electric Current

2. Flow of Charge and Electric Circuits

3. Water Flow Model High Potential Energy Water Water Pipe Height Water Doing Work Pump Doing Work Low Potential Energy Water

4. Water Flow vs. Electric Current High Potential Energy Water Water Pipe Height Water Doing Work Pump Doing Work Low Potential Energy Water

5. Electric Current Model High Voltage Electric Circuits Voltage Electric Current Doing Work Battery Doing Work Low Voltage

6. Water / Electric Current Model

7. Electric Current Model High Voltage Electric Circuits Voltage Electric Current Doing Work Battery Doing Work Low Voltage

8. Electric Current Model High Voltage Electric Circuits Electric Current Doing Work Battery Doing Work Voltage Low Voltage

9. Light Bulb Structure

10. Electric Circuit Symbols Wire Resistor Battery Voltage

11. Electric Circuits Wire Battery Resistor

12. Electric Circuits

13. Ohm’s Law

14. Electric Current Current (I) Voltage (V) Resistance (R)

15. Electric Current I (amperes , A) V (volts, V) R (ohms, Ω)

16. Ohm’s Law V I R

17. Ohm’s Law V: Voltage (V) I : Current (A) R: Resistance (Ω)

18. Voltmeter – Measuring Voltage V V

19. Ammeter – Measuring Current A A

20. Multimeter – Measuring All V: Voltage (V) I : Current (A) R: Resistance (Ω)

21. Digital Multimeter – Measuring All V: Voltage (V) I : Current (A) R: Resistance (Ω)

22. Digital Multimeter – Measuring All

23. Digital Multimeter – Measuring All Voltage / Resistance Current Ground

24. Digital Multimeter – Measuring All

25. Digital Multimeter – Measuring All Resistance DC Voltage AC Voltage DC Current AC Current Transistor

26. Ohm’s Law A V (V) I (A) R (Ω) V

27. Ohm’s Law

28. Ohm’s Law voltage = constant x current V = R x I V: Voltage (V) I : Current (A) R: Constant or Resistance (Ω)

29. Ohm’s Law V V R = orV = I R or I = I R V: Voltage (V) I : Current (A) R: Resistance (Ω)

30. Ohm’s Law Example • What is the current through a 4-ohm resistor connected to a 12-V power supply?

31. Ohm’s Law Example • What is the current through a 4-ohm resistor connected to a 12-V power supply? I = V / R I = 12 V / 4 Ω = 3 A

32. Ohm’s Law Example • A 5-ohm resistor has a 8-A current in it. What is the voltage across the resistor?

33. Ohm’s Law Example • A 5-ohm resistor has a 8-A current in it. What is the voltage across the resistor? V = I R V = 8 A x 5 Ω = 40 V

34. Ohm’s Law Example • What is the resistance of a device that uses 2.5 A of current when connected to a 15-volt power source?

35. Ohm’s Law Example • What is the resistance of a device that uses 2.5 A of current when connected to a 15-volt power source? R = V / I R = 15 V / 2.5 A = 6 Ω

36. Ohm’s Law Exercises • What is the current through a 6-KΩ resistor connected to a 9-V power supply? • What is the resistance of a device that uses 0.5 mA of current when connected to a 5-volt power source? • A 2.5-MΩ resistor has a 0.02-mA current in it. What is the voltage across the resistor?

37. Resistors

38. Resistors • A resistor is a two-terminal electronic component which implements electrical resistance • Resistors are used to control the amount of current flowing in a circuit • Resistor are usually measured by the units of Ω, kΩ, and MΩ

39. Resistors

40. Resistors on PCB

41. Resistor Color Coding

42. Surface Mount Resistors

43. SMT Resistors on PCB

44. Resistance andResistivity

45. Resistance • Electric current in a circuit is decided by voltage (V) and resistance (R): I = V / R • What are the factors to determine the resistance?

46. Resistance & Length • Which one has larger resistance?

47. Resistance & Length • Which one has larger resistance?

48. Resistance & Length • Which one has larger resistance? R ~ L

49. Resistance & Area • Which one has larger resistance?

50. Resistance & Area • Which one has larger resistance?