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Ch. 34

Ch. 34. Electric Current. Electric Current. Movement or “flow” of charge Occurs when there is a difference in voltage between the ends of a conductor Electrons carry charges through solid circuits. Electric Current ( I ). Current = charge I = q time t

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Ch. 34

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  1. Ch. 34 Electric Current

  2. Electric Current • Movement or “flow” of charge • Occurs when there is a difference in voltage between the ends of a conductor • Electrons carry charges through solid circuits

  3. Electric Current (I) Current = charge I = q time t • Measured in amperes (amps or A) Example: Calculate the current where 20 coulombs of charge pass a point in 8 seconds.

  4. Electric Current (I) Current = charge I = q time t • Measured in amperes (amps or A) Example: Calculate the current where 20 coulombs of charge pass a point in 8 seconds. 20 C / 8 s = 2.5 amps

  5. Voltage Sources • Provide a potential difference so that charges are able to flow • Examples: Dry Cells or Wet Cells • Energy from a chemical reaction is converted to electrical energy

  6. Voltage (V) • The potential energy per coulomb of charge available to electrons moving between terminals • Typical voltage in a home is 120 V • 120 Joules of energy are supplied to each coulomb of charge that flows in a circuit!!!

  7. Remember that…. Charge flows because of an applied voltage across the circuit

  8. Electric Resistance (R) Measured in ohms, Ω Depends on: • Conductivity of material • Diameter of wire • Thick wires have less resistance than thin wires • Length of wire • Longer wires have more resistance than shorter wires

  9. Ohm’s Law I = V/R Current = Voltage / Resistance Units: amps = volts / ohms

  10. I = V/R A 120 ohm heating element is powered by a 10 volt battery. What is the current?

  11. I = V/R A 120 ohm heating element is powered by a 10 volt battery. What is the current? 10 V / 120 ohm = 0.083 amps

  12. Direct Current (DC) • Charge always flow in one direction • Ex. Batteries Alternating Current (AC) • Charge alternates directions as it flows • Ex. Our outlets

  13. Since our outlets produce AC current, but many appliances use DC, what can we do…..Convert AC to DC • Diode: a converter that only allows electrons to flow in one direction

  14. Electric Power • The rate at which electrical energy is converted into another form • Power = current x voltage • P = IV

  15. Ch. 34 Practice

  16. Ch. 35 Electric Circuits • Series Circuits

  17. For Problem Solving in Series • Resistances are ADDED • R1 + R2 + R3 = R total

  18. The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown?

  19. The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown? R total = 10 + 10 + 10 = 30 ohms

  20. The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown? R total = 10 + 10 + 10 = 30 ohms If the attached voltage source is 10 V, what is the current in the circuit?

  21. The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown? R total = 10 + 10 + 10 = 30 ohms If the attached voltage source is 10 V, what is the current in the circuit? I = V/R I = 10 V / 30 ohms I = 0.33 amps

  22. Parallel Circuits 1 = 1 + 1 + 1 Rtotal R1 R2 R3

  23. Parallel Circuits The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown?

  24. Parallel Circuits The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown? 1/10 + 1/10 + 1/10 = 1 / Rtotal 0.3 = 1 / Rtotal Rtotal = 1/0.3 = 3.33

  25. Parallel Circuits The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown? Rtotal = 1/0.3 = 3.33 If the attached voltage source is 10 V, what is the current in the circuit?

  26. Parallel Circuits The resistance of one lamp is 10 ohms. What is the total resistance for the circuit shown? Rtotal = 1/0.3 = 3.33 If the attached voltage source is 10 V, what is the current in the circuit? I = V/R I = 10 V / 3.33 ohms I = 3 amps

  27. Ch. 35 Lab and Practice

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