Chapter 2

Resistive Circuits

Concept TestFor resistors in series, what is the same

for every resistor? R, V or I? Answer: I

For resistors in parallel, what is the same for every resistor? R, V or I?

Answer: V

Resistors in Series

321eq RRRR

321eq R

1

R

1

R

1

R

1

Resistors in Parallel

Voltage-divider rule “The voltage across any resistor in a series is

some fraction of the battery voltage.”

eq

totalxx R

vRv

In-Class Team ExerciseWheatstone BridgeSeries and Parallel Circuits

In-Class ProblemsP2.1(b)P2.3P2.7P2.13P2.18P2.21P2.29P2.25

Series DC NetworksTwo elements are in series if they have

only one terminal in common that is not connected to a third current carrying component.

Total Resistance

N321T R...RRRR Current through a Series

TR

EI

Consider Figure 2.29. E=24V, R1=2, R2=4, R3=6

What is RT?

What is I?What is V1, V2 and V3?

What is P1, P2, P3, and PE?

Express these numbers with only three significant figures and in the most convenient form.

0.038457 C0.0012878 A12869.578 V0.57382 W

2.7 Parallel DC NetworksTwo elements are in parallel if they have

two terminals in common.Total Resistance

N321T R

1...

R

1

R

1

R

1

R

1

Source Current

TR

EI

Example Problem 2.28Using Kirchhoff’s current law, determine

the currents I3 and I6 for the system of Figure 2.38

Consider Figure 2.32. E1=100V E2=50V E3=20V R1=10 R2=30 R3=40

What is I?What is V2?

Example Problem 2.25Find V1 and V2 of Figure 2.33 using

Kirchhoff’s voltage law.

Current-divider rule “The current through any resistor in parallel

with other resistors is some fraction of the source current.”

x

Tx R

IRI

Example Problem 2.26 Determine the following for the parallel network in Fig. 2.36.

(a) RT

(b) I (c) I2

(d) P3

Example Problem 2.29

2.8 Series-Parallel Networks

Determine the following for the network in Fig. 2.41. (a) RT

(b) I (c) I1 and I2

(d) V1

Voltage (page 13)

The term ground refers to a zero voltage or earth potential.

Ground Circuit Symbols

How Batteries WorkBattery Parts: Two different metals

separated by an electrolyte History: The first battery was created by

Alessandro Volta in 1800. He used zinc, silver and salt water to

make a voltaic pile.

Appendix B: Resistor Color Codes-2 Silver-1 Gold 0 Black1 Brown2 Red3 Orange4 Yellow5 Green6 Blue7 Violet8 Gray9 White

Tolerance 5% Gold10% Silver20% No 4th band

Memorize this table.

AnnouncementsLab Starts TodayTeams will sit together in lab

PotentiometersThey are three terminal devices with a

knob.The knob moves a slider which changes

the resistance between the terminals.Circuit Symbols: