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PH 1120 Term D, 2007 STUDY GUIDE 3
PH 1120 Term D, 2007

STUDY GUIDE 3

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/ Objective 9 Resistance and Current \
/ \
/ a) Define electric current, electric current density, drift velocity, \
/ resistance, and resistivity. \
/ \
/ b) Given two or more simple geometric shapes of a given material, \
/ compare the resistances of the shapes. \
/ \
/ c) Solve problems involving interrelationships among the quantities \
/ resistance, potential difference, current, current density, \
/ electric field, resistivity. \
/ \
/ d) Calculate the power dissipated by a resistor carrying current. \
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Suggested Study Procedure

Study Secs. 25-1, 25-2, 25-3, and 25-5. Pay attention especially to
Example 25-2. With this chapter, we officially leave
electrostatics and begin to study situations where charge is made to
move through the action of a source of emf, such as a battery. There
are a number of new terms and physical interrelationships as indicated
in the Summary at the end of Chapter 25, but the most important
interrelationship is Eqn. 25.11 which states that the product of the
resistance of a circuit element with the current flowing through it is
equal to the voltage drop across it: V = IR. Equation 25.7, a vector
equation, provides the justification for the conventional direction
chosen for current in a wire: The direction of current in a wire is
taken to be the direction that positive charges would move under the
influence of an applied field.

Suggested Problems Related to Objective 9:

Chapter 25, Problems: 1, 11, 13, 22, 42, 44

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/ Objective 10 D.C. Circuits \
/ \
/ a) Given a set of resistors in a series-parallel configuration; \
/ i) explain how current is divided among the resistors; \
/ ii) calculate the equivalent resistance of the set. \
/ \
/ b) Given a circuit consisting of voltage sources and resistors; \
/ i) calculate the current & power supplied by the sources; \
/ ii) calculate the current through, the potential drop across, and the \
/ power dissipated by any given resistor in the circuit. \
/ iii) calculate the potential difference between different points in \
/ the circuit \
/ \
/ c) Solve circuit problems involving emf and internal resistance \
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Suggested Study Procedure

Study Secs. 25-4 and 26-1, and Examples 25-9, 26-1 and 26-2 which show
how a complicated circuit can be simplified to become an equivalent
circuit with a single resistor and single source of emf.

Suggested Problems Related to Objective 10:

Chapter 25: Problems 32, 33, 36
Chapter 26: Problems 3, 4, 8, 10, 12, 13

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/ Objective 11 Multiloop and RC Circuits \
/ \
/ a) Solve multiloop circuit problems using Kirchhoff's Rules. \
/ \
/ b) Solve circuit problems involving resistor-capacitor combinations \
/ \
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Study Sec. 26-2, and Examples 26-3 through 26-7. There are
other methods of solving multiloop circuits (as EE's will learn),
however Kirchhoff's Rules represent the most fundamental as they embody
conservation of charge (the Junction Rule) and conservation of energy
(the Loop Rule). We will briefly discuss electrical instruments in
lecture, so you can take a look at sec. 26-3 if you are interested.
Read section 26-4 on circuits with both resistors and capacitors.

Suggested Problems Related to Objective 11:

Chapter 26, Problems: 19, 20, 21, 22, 36, 38, 63, 68



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/ Objective 12 Magnetic Forces \
/ \
/ a) For two vectors given in i j k notation, calculate the vector \
/ product (cross product). \
/ \
/ b) Given the charge, mass, and initial velocity of a particle \
/ traveling through specified electric and magnetic fields, \
/ determine the force on the particle and its acceleration. \
/ \
/ c) Analyze the circular motion of charged particles moving in a \
/ magnetic field. \
/ \
/ d) Given a current carrying wire located in a magnetic field, \
/ determine the force exerted on a length L of this wire. \
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Suggested Study Procedures

Review the definition of cross product on pages 27-30 in Chapter
1 very carefully and study Example 1-12. Study Sec. 27-1, 27-2,
27-4, 27-5, 27-6, 27-7. Study carefully the relative directions of the three mutually
perpendicular vectors in Fig. 27-6. Study Examples 27-1, 27-3,
27-5, and 27-7.

The Hall effect is an important and useful application of the material
in this Objective, and it will be discussed in lecture. Look over Sec.
27-9 to see how this phenomenon can be applied to semiconductors.

Suggested Problems Related to Objective 12:

Chapter 27, Problems: 1, 2, 5, 6, 15, 20, 29, 33, 36, 40


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HOMEWORK ASSIGNMENTS FOR STUDY GUIDE 3
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Homework Assignment #9 - due at 4:00 pm Monday, April 9


Just as with Homework #7, this assignment is to be submitted via the web. In your web browser, go to
www.masteringphysics.com
. Then login using the username and password you have chosen.

After logging in, click on Assignment List and select Homework #9. If you need any review, you can always
do that by repeating Assignment 0, a brief, noncredit tutorial on how to enter answers in Mastering Physics.

In Homework #9, you will get 6 chances to submit a correct answer for each problem. If your first answer is
incorrect, you should consider making use of the hints.



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Homework Assignment #10 - due in lecture Wednesday, April 11

1. An automobile battery has an emf of 12.6 V and an internal resistance
of 0.080 . The headlights have a total resistance of 5.00 (assumed
constant). What is the potential difference across the headlight
bulbs (a)when they are the only load on the battery, and (b)when the
starter motor, which takes an additional 35.0 A from the battery, is
operated?

2. In the circuit shown, (a)Find the
equivalent resistance between points
a and b , and (b)Calculate the
current in each resistor if a
potential difference of 34.0 V is
applied between points a and b.









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Homework Assignment #11 - due in lecture Friday, April 13

1. The ammeter shown in the figure to
the right reads 2.00 A. Find I
1
, I
2
,
and .












2. A 2.00-nF capacitor with an initial charge of 5.10 µC is discharged
through a 1.30 k resistor. (a)Calculate the current through the
resistor 9.00 µs after the resistor is connected across the terminals
of the capacitor. (b)What charge remains on the capacitor after 8.00
µs? (c)What is the maximum current in the resistor?

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