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Electrical Quantities

Electrical Quantities. Arch 433– Electrical Systems. Goals. To understand the basic terminology of electricity Be able to make basic electrical calculations. Current Flow – Direction?. Electron Theory Most negative to positive (EurAsia) Most widely accepted as being correct

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Electrical Quantities

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  1. Electrical Quantities Arch 433– Electrical Systems

  2. Goals • To understand the basic terminology of electricity • Be able to make basic electrical calculations

  3. Current Flow – Direction? • Electron Theory • Most negative to positive (EurAsia) • Most widely accepted as being correct • Conventional Theory • Most positive to most negative (US/Canada) • Negative considered as ground • Positive as “HOT” • Schematics are drawn from top down (positive to negative

  4. Electrical Quantities • Coulomb – (kü-läm-lōm) • Amp • Volt • Ohm • Watt • Horsepower • BTU

  5. Electrical Quantities • Can humans create electricity? • You would not be reading this if you didn’t produce electricity

  6. Electrical Systems • Electrical charges jump from one cell to another in lieu of wires until they reach their destination. • According to the Center for Space Power and Advanced Electronics, the human body is capable of producing 11,000 watt hours.

  7. Electrical Systems • How many watts • 81 watts sleeping. • 128 standing at ease. • 163 walking. • 407 briskly walking • 1,048 long-distance runner. • 1,630 from a sprinter.

  8. The Coulomb cou·lomb • A quantity of measurement similar to a quart, gallon, liter, etc. • It takes a certain amount of liquid to fill a gallon • One Coulomb = 6.25 x 1018 electrons • It takes a certain amount of electrons to equal a Coulomb One Coulomb = 6,250,000,000,000,000,000 electrons 6.25 Quintillion

  9. The Coulomb • Coulomb's law or Coulomb's inverse-square law is a law of physics describing the electrostatic interaction between electrically charged particles. It was first published in 1785 by French physicist Charles Augustin de Coulomb and was essential to the development of the theory of electromagnetism.

  10. Charles Augustin de Coulomb He liked to be called “Chuck” and to his friends, “Chucky C”

  11. The Amp “I” • Defined -One Coulomb per sec • Note: involves a quantity and a time • One amp of current flows through a wire when one coulomb flows past a point in one second • Noted as intensity of current or (“juice”, “current”, electron “flow”)

  12. The Amp “I” • So Current is the flow…the flow of water • Current (I) is equivalent to the flow rate, and the resistance is like the pipe size. • Increase the pressure, more water comes out of the hose. • Increase the diameter of the hose and more water comes out of the hose

  13. The Amp “I” (cont.) Speed? • A single electron moves at a rate of 3 inches per hour at one ampere of current flow • This is about as fast as my wife.

  14. The Amp “I” (cont.) • The impulse of electricity can appear to be faster than the speed of light • Knowing the speed of one electron, how can this be? When a ball (electron) is pushed at one end, another ball (electron) at the other end is forced out. There are billions of electrons in a wire – get the idea of the impulse of electricity?

  15. The Amp “I” (cont.) • It’s like a line dance!

  16. The Amp “I” (cont.) If a copper wire was wrapped around the globe 10 times, it would take about 1.3 seconds to turn the light on at the other end. How do I know this?

  17. Boat

  18. Dessert

  19. Bar

  20. The Volt “E” • Defined as electromotive force or EMF Voltage cannot flow • It is like pressure in a water system • Voltage pushes current through a wire but DOES NOT “flow” though a wire

  21. The Ohm “” or “R” • The unit of resistance to current flow • An ohm is the amount of resistance that allows 1 amp of current to flow when the applied voltage is 1 volt • Like a reducer in a water pipe or rough pipe vs smooth pipe – restricts flow

  22. The Ohm “” or “R” (cont.) • Heat caused by the flow of current • Energy lost due to electron contact • Resistance (similar to friction heat)

  23. The Watt “P” • A function of both voltage and amps • “push” and “amount of juice” • Known as “power” • Wattage is not a flow of current, it is a resulting amount of power • Before true power can exist, there must be some type of energy change or conversion • Heat (light bulb) • Mechanical (steam generator)

  24. The Watt “P” • Where did the term Watt come from? • Actually you could say it came from horses. • Before we had electricity we had horses working. • Plowing fields and pulling carriages and the like.

  25. The Watt “P” • And making a lot of horse poop. Or a lot of horse crap …..or horse sh…. • However the word “lot” was confused with “watt” as is in “a watt of crap” and the term stuck. • So when electricity was invented we converted horsepower to the term “watt”.

  26. The Watt “P” What (or watt) do you think? Could this be possible true?

  27. The Watt “P” It’s false. Class, meet Mr. James Watt Hello class….I like horses

  28. Horsepower • James Watt needed to sell his steam engines he was making. • So he put power in the term that people would understand being horsepower • After experimentation, he found that the average horse can work steady pulling a plow at 550 foot-pound per second* • Doing the math, this would equate: • 1 hp = 746 W *the amount of force required to raise one pound of weight one foot

  29. Horsepower • So the term watt used in electricity originated with James Watt trying to find a way to measure something people at the time understood which was “horse power”. Horse power is the amount of power an average plow horse can exert.

  30. Quiz Question • Where does the term “All balls out” come from? a) Ballroom dancing b) A word used in the movie Animal House. c) A part of the male anatomy d) Firemen e) None of the above

  31. BTU – British Thermal Unit • Defined • The amount of heat required to raise the temperature of one pound of water one degree Fahrenheit • In metric terms, the joule is equivalent to a watt • 1 watt = 3.412 BTU per hour • 1 kilowatt (kw) = 3412 BTU per hour

  32. James Prescott Joule I’m such a STUD

  33. Conversion Chart - Power Common Power Units

  34. Electrical Quantities E = Volts I = Amps R = Resistance (Ohms  ) P = Watt

  35. Ohm’s Law • Defined • It takes one volt to push one amp through one ohm • E = I x R • I = E/R • R = E/I

  36. Georg Simón Ohm Go Cougs!

  37. Formula Chart

  38. Ohm’s Law

  39. Examples R = 144 100 W V or E = voltage, I = current, R = Resistance A light bulb rated at 100 watts. The bulb operates at 120 volts What is its current flow? What is the resistance of the filament? I = 0.83 100w/120v = 0.83 ampere 120v/0.83a = 144 ohms, or 1202/100W = 144 ohms

  40. Example (cont.) R = 48 300 W • A light bulb rated at 300 watts. The bulb operates at 120 volts What is its current flow? What is the resistance of the filament? I = 2.5 300w/120v = 2.5 ampere 120/2.5 = 48 ohms, or 1202/300W = 48 ohms

  41. Example (cont.) • 100 watt bulb has • 0.83 amp current flow • 144 ohms of resistance • 300 watt bulb has • a bigger filament than 100 watt bulb thus • 2.5 amp current flow • 48 ohms of resistance * A bigger filament means less resistance to electron flow. This equates to more electrons passing through the filament thus creating a more intense light

  42. Practice Problems • An electric heating element has a resistance of 9.6  and is connected to a voltage of 120 V. How much current will flow in this circuit? • Using the above question, how many watts of heat are being produced by the heating element? • A 240 V circuit has a current flow of 20 A. How much power is connected in the circuit? • An electric motor has an apparent resistance of 15 . If 8 A of current are flowing through the motor, what is the connected voltage? 120v/9.6 = 12.5 A (12.5 A)(120 V) = 1500 W (240 V) (20 A) = 4800 W (8 A)(15 ) = 120 V

  43. Practice Problems (cont.) • You plan to install a 5 kW electric heating unit in your home. You want to operate the unit in the most efficient way. Would you connect the unit to a 120 V or 240 V electrical system? • In the above, which voltage system is the most expensive to operate? Uses the most power? Uses the most amperage? Uses the larger conductors? 5000 W/ 120 V = 41.67 A 5000 W / 240 V = 20.8 A Use same amount of power 120 V uses a larger current thus larger conductors

  44. Problems (cont.) • A conductor has a resistance of 20 ohms per 1000 feet of length. The conductor serves a lamp 200 feet from the power source. If lamp has a resistance of 72 ohms and a source voltage of 120, what is the voltage drop across the light bulb? • First find ohms or resistance • Next circuit current • Next voltage drop through the conductors • Finally find actual voltage across the lamp

  45. Problems (cont.) 4 + 72 + 4 = 80 ohms 120 V = (I)(80 ohms) I = 1.5 A E = 1.5 A (4 + 4) = 12 volts drop E = (1.5)(72) = 108 volts

  46. Questions On a full sheet of paper and working with anyone directly next to you place your names on that sheet. Answer the following questions. • What is the maximum number of duplex outlets that can be served by a single 20 ampere, 120 volt circuit.

  47. Going Bald……. Can cause psychological issues The research shows hair loss can cause: • 62% of men affect their • self-esteem • 43% of men to be concerned with their attractiveness • 37% of men to be worried about getting older • 22% of men to be anxious about their social life • 21% percent to become depressed

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