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Electronics

Electronics. Ohm’s Law. 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. Terms and Definitions.

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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!

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