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Electricity

Electricity. Chapter 6. Fiat lux! (Then there was light!). The generator, battery, or power pack supplies the energy…. Fiat lux! (Then there was light!). …the wire carries a charge…. Fiat lux! (Then there was light!). …the electrical potential energy is converted into heat and light….

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Electricity

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  1. Electricity Chapter 6

  2. Fiat lux!(Then there was light!) The generator, battery, or power pack supplies the energy…

  3. Fiat lux!(Then there was light!) …the wire carries a charge…

  4. Fiat lux!(Then there was light!) …the electrical potential energy is converted into heat and light…

  5. Fiat lux!(Then there was light!) …and the charge must be allowed to return to its source.

  6. Fiat lux!(Then there was light!) The potential energy is measured in Volts.

  7. Fiat lux!(Then there was light!) The charge is measured in Coulombs

  8. Fiat lux!(Then there was light!) The power of the bulb is measured in Watts.

  9. Fiat lux!(Then there was light!) The flow of charge is measured in Amperes.

  10. How did you get your bulb to light? • You made a circuit • You provided the work. The generator converted it into electrical energy. • Electrons (- charge) moved through the wires, heated up the filament in the bulb, and returned to the generator.

  11. Things to measure: Charge Voltage Current Resistance Power Energy

  12. Things to measure: Charge (q) Voltage (V) Current(I) Resistance(R) Power(P) Energy(E)

  13. Things to measure: Charge (q) in Coulombs Voltage (V) in volts Current(I) in amps Resistance(R) in ohms Power(P) in Watts Energy(E) in Joules

  14. Things to measure: Charge (q) in Coulombs (C) Voltage (V) in volts (V) Current(I) in amps(A) Resistance(R) in ohms() Power(P) in Watts(W) Energy(E) in Joules(J)

  15. Measure the current and voltage • V=___ V I=____ A A V

  16. Resistance • --the resistance to the flow of charge Resistance=Voltage/Current

  17. Resistance • --the resistance to the flow of charge R=V/I

  18. Resistance • Measure the current and voltage. • V=___ V I=____ A R=V/I=____

  19. Warning! • Not all bulbs are identical. • Their resistance varies with brightness!

  20. Try a different bulb. • Measure the current and voltage. • V=___ V I=____ A R=V/I=____

  21. Make a table

  22. A A A A A V V V V V

  23. ?R V=6.0 V I=2.0 A

  24. ?R I=3.0 A I=2.0 A V=12.0 V V=6.0 V I=2.0 A I=4.0 A V=9.0 V V=12.0 V

  25. ?I R=2.0  R=2.0  V=6.0 V V=12.0 V R=4.0  R=12.0  V=6.0 V V=6.0 V

  26. ?V R=2.0  R=2.0  I=.60 A I=6.0 A R=4.0  R=12.0  I=2.0 A I=.50 A

  27. A A A A A V V V V V

  28. Series and Parallel Measure the current and voltage of each circuit A A V V

  29. Series and ParallelWhich is which?

  30. Series and ParallelWhich is which?

  31. Series circuit • Voltage is split between the bulbs. • Current is the same • Addthe resistances

  32. Parallel circuit • Voltage is the same for each leg • Current splits into each leg. • Resistance goes down

  33. Voltage is split between the bulbs. Current is the same Add the resistances Voltage is the same for each leg Current splits into each leg. Resistance goes down • RTotal=R1+R2 • 1/RTotal=1/R1+1/R2

  34. Power P =IV = I2R =V2/R

  35. Power P =IV =(C/s)(J/C) = I2R =(C2/s2)(J/C)/(C/s) =V2/R =(J2/C2)/((J/C)/(C/s))

  36. Power P =IV =(C/s)(J/C) =J/s = I2R =(C2/s2)(J/C)/(C/s) =J/s =V2/R =(J2/C2)/((J/C)/(C/s)) =J/s

  37. Power P =IV =(C/s)(J/C) =J/s=W = I2R =(C2/s2)(J/C)/(C/s) =J/s=W =V2/R =(J2/C2)/((J/C)/(C/s)) =J/s=W

  38. Power P =IV =(C/s)(J/C) =J/s=W = I2R =(C2/s2)(J/C)/(C/s) =J/s=W =V2/R =(J2/C2)/((J/C)/(C/s)) =J/s=W The units of power are Watts

  39. Home wiring A panel of circuit breakers allows only up to some maximum current through each circuit in the house. If you plug in too many things, it breaks the circuit.

  40. A typical house: • Houses are wired with 240 V. This is stepped down with a transformer to 120 V for most circuits. • The highest power appliances (stove, AC, dryer, water heater) might use 240 V circuits.

  41. A typical house: • The US average electrical use in a home is about 1200 W. • What causes variation in load?

  42. A typical house: • The US average electrical use in a home is about 1200 W. • What causes variation in load? • Most homes can carry over 100 A safely.

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