Model of Current
Charge Carriers in Metals are Electrons
Creating Current
Conservation of Current
Law of Conservation of Current – The current is the same at all points in a current carrying wire.
Defining and Describing Current
Definition of Current
Units: 
Direction of Conventional Current is the direction the positive charge carriors would travel.
Conservation of Current at a Junction
Kirchoff's Junction Law – the sum of the currents coming into a junction equals the sum of the currents leaving a junction.
Example 1
The disk drive in a portable CD player is connected to a battery that supplies it with a current of 0.22 A. How many electrons pass through the drive in 4.5 s?
Example 2
The currents through several segments of
a wire object are shown in the figure below. What are the magnitudes and
directions of the currents 
and 
in
segments B and C?
Batteries and EMF
Connecting Potential and Current
Factors that affect the current in a wire
Resistance (R) – Opposition of a circuit to the flow of electric current.
Example 3
A potential difference of 24 V is applied
to a 150 
resistor.
How much current flows through the resistor?
Resistance
Where L is length of the wire, A is the
cross-section area, and 
is
the material resistivity (Table 22.1 p. 732)
Example 4
Wire 1 has a length and a circular cross section of diameter D. Wire 2 is constructed from the same material as wire 1 and has the same shape, but its length is 2L, and its diameter is 2D. Is the resistance of wire 2 (a) the same as that of wire 1, (b) twice that of wire 1, or (c) half that of wire 1?
Example 5
A current of 1.82 A flows through a copper wire 1.75 m long and 1.10 mm in diameter. Find the potential difference between the ends of the wire.
Resistors and Ohm's Law
Ohmic and Nonohmic Materials
Energy and Power
In general, energy is required to cause an electric current to flow through a circuit. The rate at which the energy must be supplied is the power.
or
or
Example 6
A handheld electric fan operates on a 3.00 V battery. If the power generated by the fan is 2.24 W, what is the current supplied by the battery?
Example 7
A battery that produces a potential difference V is connected to a 5 W light bulb. Later, the 5 W light bulb is replaced with a 10 W light bulb. (a) In which case does the battery supply the greatest current? (b) Which light bulb has the greatest resistance?
Example 8
A battery with an emf of 12 V is connected
to a 545 resistor.
How much energy is dissipated in the resistor is 65 s?
Energy Usage
Example 9
A holiday goose is cooked in the kitchen oven for 4.00 h. Assume that the stove draws a current of 20.0 A, operates at a voltage of 220.0 V, and uses electrical energy that costs $0.048 per kWh. How much does it cost to cook your goose?