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Example:
In the given circuit:
(a) How much power is drawn from the battery?
(b) How much current flows through each resistor? And in what
direction?
Example:
(a) A 34.5m length of copper wire at 20.0°C has a radius of 0.25
mm. If a potential difference of 9.0V is applied across the
length of the wire, determine the current in the wire. (b) If the
wire is heated to 30.0°C while the 9.0V potential difference is
maintained, what is the resulting current in the wire?
Resistivity of Cu =1.72x10-8 Ω·m
at 20 C0,
temperature coefficient: α =3.93 x10-3 C-1
Example The Power and Energy Used in a Flashlight
In the flashlight, the current is 0.40A and the voltage of each of
two cells is 1.5 V. Find (a) the power generated by each cell, (b) the
power consumed by the bulb, and (c) the energy dissipated in the
bulb in 5.5 minutes of operation.
(a) This is a single-loop circuit with no branch points. The 0.40A
current flows through the entire circuit, while the potential
difference across EACH cell is 1.5 V
Example:
Using Kirchhoff’s Loop Rule, determine the current in the circuit.
Example:
Using Kirchhoff’s Rules, determine the power
consumed by each of the 3 resistors
The circuit in the figure contains a battery and a resistor in series.
Which of the following statements is not true?
A) The current in the circuit is 2 A.
B) Point α is at a higher potential than point β, and VαB = 5 V.
C) The battery is supplying energy to the circuit at the rate of 6 W.
D) The rate of heating in the external resistor is 10 W.
If a current of 2.0 A is flowing from point a to point b, the potential difference
between the points is
A) 6 V
B) 8 V
C) 14 V
D) 20 V
E) 22 V
 2 A  3  20V  2 A 1  6V  6V