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Electronics

Electronics

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Electronics

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  1. Electronics Ohm’s Law

  2. Presentation Overview • Terms and definitions • Letters and terms used in Ohm’s Law • Ohm’s Law • Use of the Ohm’s Law circle • Applications of Ohm’s Law

  3. Terms and Definitions • Voltage- electrical potential; an electrical pressure created by the buildup of charge; causes charged particles to move • Volt- unit of voltage; Symbol= V • Electromotive force- ahistorical term used to describe voltage; Symbol= E • (No longer relevant, the definition of force is something that causes a mass to accelerate, and voltage or EMF does not fit that definition). E is now commonly used as a symbol for electric field strength. • Current- the flow or movement of electrons • Ampere- unit of current; Symbol= I • Resistance- opposition to current flow • Ohm- unit of resistance; Symbol= Ω(Greek symbol Omega)

  4. Terms and Definitions (continued) • Energy- the fundamental ability to do work • Joule- unit of energy; Symbol= J • Electrical Power- the rate of electrical energy used in a circuit; calculated by multiplying current times voltage, or P = V • I • Watt- unit of measurement for power; a watt is one joule per second (J/s); Symbol= W • Ohm’s Law- a formula describing the mathematical relationship between voltage, current, and resistance; one of the most commonly used equations in all of science

  5. Terms and Definitions (cont) • Directly proportional- having a constant ratio; a situation where one variable moves in the same direction as another variable when other conditions are constant • Inversely proportional- having a constant but inverse ratio; a situation where one variable moves in the opposite direction from another variable when other conditions remain constant • Example- current doubles when voltage is doubled if resistance is held constant; thus, voltage and current are directly proportional • Example- with a constant voltage, current decreases when resistance increases; thus, current and resistance are inversely proportional

  6. Review of Letters and Terms used in Ohm’s Law • I – Electrical current in amperes • R – Resistance in ohms • V – Represents voltage in volts • A – Represents amperes • Ω– Represents ohms • E – Electromotive force (emf) in volts, sometimes used as an alternate symbol for voltage

  7. Ohm’s Law • A mathematical formula typically expressed as, (Read as “current equals voltage divided by resistance.”) • This formula can be rearranged in two more ways: and

  8. The Ohm’s Law Circle

  9. Using The Ohm’s Law Circle • Cover the value you want to solve for • The remaining two terms give the equation

  10. Example One • Solve for Current

  11. Example One • Cover the current symbol

  12. Example One • Cover the current symbol

  13. Example One • Cover the current symbol Current equals voltage divided by resistance

  14. Example Two • Solve for Voltage

  15. Example Two • Cover the voltage symbol

  16. Example Two • Cover the voltage symbol

  17. Example Two • Cover the voltage symbol Voltage equals current times resistance

  18. Example Three • Solve for Resistance

  19. Example Three • Cover the resistance symbol

  20. Example Three • Cover the resistance symbol

  21. Example Three • Cover the resistance symbol Resistance equals voltage divided by current

  22. Three Forms of Ohm’s Law 1. Calculating circuit resistance Example: R = V / I 2. Calculating circuit amperage Example: I = V / R 3. Calculating circuit voltage Example: V = IR

  23. One Way To Visualize Ohm’s Law Ohm’s Law One volt is required to push one amp through one ohm resistance. E = IR Volts = Amperes x Ohms

  24. Common Metric Values Ohm’s Law uses results in both large and small numbers, so a review of metric prefix values is important.

  25. Practice Problem One • You have a circuit with a source voltage of 12 V DC and a circuit resistance of 150 Ω. Solve for the unknown value using Ohm’s Law.

  26. Practice Problem One • You have a circuit with a source voltage of 12 V DC and a circuit resistance of 150 Ω. Solve for the unknown value using Ohm’s Law. • To solve, first write down all values V = 12 v R = 150 Ω I = ?

  27. Practice Problem One • Next, look at the Ohm’s Law Circle V = 12 v R = 150 Ω I = ?

  28. Practice Problem One • Cover what you are solving for V = 12 v R = 150 Ω I = ?

  29. Practice Problem One • Cover what you are solving for V = 12 v R = 150 Ω I = ?

  30. Practice Problem One • Cover what you are solving for V = 12 v R = 150 Ω I = ? I = 0.08 A

  31. Summary of Problem One or I = 80 mA

  32. Practice Problem Two • You have a circuit with a source voltage of 9 V DC and a circuit resistance of 360 Ω

  33. Practice Problem Two • You have a circuit with a source voltage of 9 V DC and a circuit resistance of 360 Ω • Write down all of the values V = 9 v R = 360 Ω I = ?

  34. Practice Problem Two • You have a circuit with a source voltage of 9 V DC and a circuit resistance of 360 Ω • Write down all of the values V = 9 v R = 360 Ω I = ?

  35. Summary of Problem 2 V = 9 v R = 360 Ω I = ? or I = 25 mA

  36. Practice Problem Three • You have a circuit with a resistance of 900 Ω and a current of 30 mA

  37. Practice Problem Three • You have a circuit with a resistance of 900 Ω and a current of 30 mA R = 900 Ω I = 30 mA V = ?

  38. Practice Problem Three • You have a circuit with a resistance of 900 Ω and a current of 30 mA R = 900 Ω I = 30 mA V = ?

  39. Practice Problem Three • You have a circuit with a resistance of 900 Ω and a current of 30 mA R = 900 Ω I = 30 mA V = ?

  40. Summary of Problem Three R = 900 Ω I = 30 mA V = ? or V = 27 v

  41. Practice Problem Four I = 59 mA V = 19 v R = ?

  42. Practice Problem Four I = 59 mA V = 19 v R = ?

  43. Practice Problem Four I = 59 mA V = 19 v R = ?

  44. Practice Problem Four I = 59 mA V = 19 v R = ?

  45. Presentation Summary • Terms and definitions • Letters and terms used in Ohm’s Law • Ohm’s Law • Ohm’s law in circular expression • Use of Ohm’s Law Let’s do some problems!