Ph-204 Chap 22 Current and Resistance

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Ph-204 Chap 22 Current and Resistance
2013-02-20 13:21:10
Physics Chapter 22 Current Resistance

Current and Resistance
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  1. Current (Ι)is defined to be:
    • the motion of positive charges.
    • I=Δq/Δt
  2. emf:
    is the potential difference of the battery.  The battery does work to raise the potential of the charges.
  3. Conservation of current:
    Dictates that the current is the same at all points in the circuit.
  4. A battery is:
    a source of potential difference.  Chemical processes in the battery separate charges.  We use a charge escalator model to show the lifting of charges to higher potential.
  5. The actual charge carriers are:
    electrons.  Their random collisions with atoms impede the flow of charge and are the source of resistance.  The collisions increase the thermal energy of the resistor.
  6. We use the ideal wire model in which:
    we assume that there is no resistance in the wires.
  7. The resistivity p is a property of a material:
    • a measure of how good a conductor the material is.
    • Good conductors have low resistivity.
    • Poor conductors have high resistivity.
  8. Resistance is:
    • The property of a particular wire or conductor.  It depends on its resitivity and dimensions. 
    • R=ρL/A
  9. Ohm's Law:
    • describes the relationship between potential difference and current in a resistor. 
    • I=ΔV/R
  10. A battery supplies power at the rate:
  11. The resistor dissipates power at the rate:
  12. Define Ohmic:
    When a potential difference is applied to a wire, if the relationship between potential difference and current is linear, the material is Ohmic.
  13. Resistors are:
    • made of ohmic materials and have a well-defined value of resistance: 
    • R=ΔV/I
  14. If the variation is not linear then the material is: