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Electric Current, Circuits, Resistance and Ohm’s law

Electric Current, Circuits, Resistance and Ohm’s law. MHR pg. 619-632. What is Electric Current?. An electric current is: the movement of electrons ( think of a water current- movement of water)

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Electric Current, Circuits, Resistance and Ohm’s law

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  1. Electric Current, Circuits, Resistance and Ohm’s law MHR pg. 619-632

  2. What is Electric Current? • An electric current is: • the movement of electrons ( think of a water current- movement of water) • These electrons carry energy ( in volts) and can transfer their energy to a load such as a light bulb

  3. Formula for Current • I = Q / Δt • Where • I = current ( amps) • Q = amount of charge ( coulombs) • Δt = change in time ( seconds)

  4. Problem #1: Cell phone chargers • What is the current travelling through a cell phone charger when 0.20 mC of electrons pass a point in 0.75 min? • Answer: • 4.4 x 10 -6 A

  5. How do you measure electric current? • Review. • What is going on with the diagram below? • Where would you put the ammeter? • Follow the symbols pg. 619 in your text book How bright are the two light bulbs?

  6. Analyse this circuit: The ammeter goes ______the first light bulb. How bright are the two light bulbs?

  7. How much energy does each light bulb absorb? • Measure the voltage ( change in energy) across each light bulb in the circuit below: The light bulb that is brighter has more or less energy?

  8. How much energy does each light bulb absorb? • Measure the voltage ( change in energy) across each light bulb in the circuit below: How bright are the light bulbs? How much energy does each light bulb require?

  9. Electrical Resistance (R) • Electrical Resistance: is a measure of how difficult it is for an electrical current to travel through a material • High resistance materials: do not allow an electric current to pass through ( example: plastic) • Low resistance materials: allow electric current to pass through ( example: copper)

  10. Resistor • An electrical device that has a specific resistance • The units for resistor is ohms or Ώ

  11. Ohm’s Law • If you were to graph the amount of energy the electrons transfer to a load (V) vs the flow of electrons that pass through a load (I), the graph would look like this:

  12. Take their slope!!!! So what do we do with straight lines?

  13. Where : R= resistance ( Ώ) V = potential difference ( V) I = current ( A) Ohm’s Law

  14. Your Turn… • Read pg. 622-625 • MHR pg. 632 # 21-26 ( blue background) • MHR pg. 632 # 1,2 ( yellow background)

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