Ph-204 Chap 22 Current and Resistance

• the motion of positive charges.
• I=^Δq/_Δt

is the potential difference of the battery.  The battery does work to raise the potential of the charges.

Dictates that the current is the same at all points in the circuit.

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.

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.

we assume that there is no resistance in the wires.

• a measure of how good a conductor the material is.
• Good conductors have low resistivity.
• Poor conductors have high resistivity.

• The property of a particular wire or conductor.  It depends on its resitivity and dimensions. 
• R=^ρL/_A

• describes the relationship between potential difference and current in a resistor. 
• I=^ΔV/_R

P_emf=Iε

P_R=IΔV_R=I²R=(ΔV_R)²/R

When a potential difference is applied to a wire, if the relationship between potential difference and current is linear, the material is Ohmic.

• made of ohmic materials and have a well-defined value of resistance: 
• R=^ΔV/_I

Nonohmic.