20.3 Complex Resistor Combinations
Date, Section, Pages, etc.
Mr. Richter
Agenda
 Warm-Up
 Review HW
 p. 744 #1-4
 p. 745 #1-6
 Complex Resistor Combinations
 Complex Circuit Problem Solving
 Equivalent Resistance
 Current and Voltage Drops
Objectives: We Will Be Able To…
 Determine the equivalent resistance of a complex resistor
combination.
 Determine the current through and voltage drop across a
resistor within a complex resistor combination.
Warm-up
 Calculate the equivalent resistance of an 8.0 Ω resistor and a
4.0 Ω resistor arranged in parallel.
Complex Resistor Combinations
Complex Resistor Combinations
 Most circuits are not purely
series circuits or purely
parallel circuits.
 Most circuits are a
combination of series and
parallel circuits.
Equivalent Resistance
Equivalent Resistance
 To determine the equivalent resistance in a complex circuits:
1. Redraw the circuit in a line.
2. Combine all resistors in series and redraw
3. Combine all resistors in parallel and redraw
4. Repeat
Equivalent Resistance:
Redraw the Circuit in a Line
=
Equivalent Resistance:
Resistors in Series
6.0 Ω
3.0 Ω
2.0 Ω
6.0 Ω
4.0 Ω
1.0 Ω
Equivalent Resistance:
Resistors in Series
8.0 Ω
6.0 Ω
2.0 Ω
3.0 Ω
6.0 Ω
9.0 Ω
4.0 Ω
1.0 Ω
Equivalent Resistance:
Resistors in Parallel
8.0 Ω
1.0 Ω
9.0 Ω
4.0 Ω
Equivalent Resistance:
Resistors in Parallel
8.0 Ω
1.0 Ω
9.0 Ω
2.7 Ω
4.0 Ω
Equivalent Resistance:
Repeat (Resistors in Series)
1.0 Ω
9.0 Ω
12.7
2.7ΩΩ
Current and Voltage Drops
Current and Voltage Drops
 To find the current through and voltage drop across a
specific resistor, work your way back from the equivalent
resistors!
1. Calculate the current.
2. Then the voltage drops.
3. Redraw and repeat.
3.0 Ω
6.0 Ω
12.7 Ω
6.0 Ω
2.0 Ω
=
4.0 Ω
1.0 Ω
Current and Voltage Drops
I = 0.71 A
9.0 Ω
12.7 Ω
1.0 Ω
2.7 Ω
Current and Voltage Drops
I = 0.71 A
9.0 Ω
1.0 Ω
2.7 Ω
V = 1.9V
Current and Voltage Drops
V = 1.9V
8.0 Ω
1.0 Ω
9.0 Ω
2.7 Ω
4.0 Ω
Current and Voltage Drops
V = 1.9V
I = 0.24 A
8.0 Ω
6.0 Ω
2.0 Ω
1.0 Ω
9.0 Ω
4.0 Ω
Current and Voltage Drops
I = 0.24 A
6.0 Ω
V = (0.24 A)(2.0Ω)
V = 0. 48 V
2.0 Ω
1.0 Ω
9.0 Ω
4.0 Ω
Wrap-Up: Did we meet our objectives?
 Determine the equivalent resistance of a complex resistor
combination.
 Determine the current through and voltage drop across a
resistor within a complex resistor combination.
Homework
 Due Thursday:
 p. 752 #1-9