PHYSICS 51: Review Ch 21-24
RICHARD CRAIG
Plan for the day
Exam format and rules
Some Basic Ideas from E&M
Examples of conceptual problems
Conceptual problems from practice test
Short break
More advanced ideas
Practice Test
Exam format and rules
Closed bo
Answer Key
Phy 9C Quiz 2
Name: _
Student ID: _
1. (12 pts) A solid conducting sphere with radius carries a positive total charge . The sphere is
surrounded by an insulating shell with inner radius and outer radius . The insulating shell has a
uniform char
Discussion 4 Problem 24.11(9)
In the book: Sections 24.1, 23.2 & 23.3, Examples 22.6, 23.10, 24.4
24.11 A capacitor is made from two hollow, coaxial, iron cylinders, one inside the other. The inner cylinder is
negatively charged and the outer is positivel
CheckPoint: Gaussian Surface Choice
You are told to use Gauss' Law to calculate the electric field at a distance R away from
a charged cube of dimension a. Which of the following Gaussian surfaces is best suited
for this purpose?
o a sphere of radius R+1/
Announcements
Equipotential Homework:
Only do first two problems
Problem 3 (Potential of Concentric Cylindrical Insulator and
Conducting Shell) and Problem 4 (Potential of Infinite Sheets
of Charge and Conducting Slab) are not worth credit and will
not
Clicker Question: Trapezoid in Constant Field
E = E0 x
y
Label faces:
1: x = 0
2: z = +a
3: x = +a
4: slanted
3
1
2
x
Define Fn = Flux through Face n
z
A)
F1 < 0
A)
F2 < 0
A)
F3 < 0
A)
F4 < 0
B)
F1 = 0
B)
F2 = 0
B)
F3 = 0
B)
F4 = 0
C)
F1 > 0
C)
F2 > 0
C)
CheckPoint: Field Lines - Two Point Charges 1
Compare the magnitudes of the two charges
o |Q1| > |Q2|
o |Q1| = |Q2|
o |Q1| < |Q2|
o There is not enough information to determine the relative magnitudes of
the charges.
Electricity & Magnetism Lecture 3, Sli
Announcements
Quiz 3 moved to May 7
Quiz 1 Regrade requests due today at 5pm. (mailroom Phy 173)
Grades so far
Quiz 1
Avg: 7.12
Std Dev: 4.43
Quiz 2
Avg. 8.58
Std Dev: 4.09
Results are pretty dismal. Time for a mid-course correction.
The smartPhysic
Announcements
Chapter 25 Reading Assignment:
Sections 25.1-25.5 except
Resistivity and Temperature pg 824
Example Problems: 2, 5-10
Problem-Solving Strategy 25.1: Power and Energy in
Circuits
Quiz 1 Regrade Requests will be returned on Friday
Quiz 2 R
Announcements
Quiz 3 on Monday
Midterms back at end of class
Colin Cunliff
Electricity & Magnetism Lecture 12, Slide 1
Skinny
Wire
Fat Wire
1
2
Two wires of equal length and identical metals but
different diameters are connected to identical batteries.
Co
Announcements
Midterm 1 regrade requests due Friday, 5/11 at 5pm
Pick your regrade requests for Quiz 1 and 2 at the end of class.
Midterm 2 scheduled for Monday, May 14!
University Physics Ch 24-26,
smartPhysics units 7-11
Midterm 2 review session c
Announcements
Pick up a worksheet for problem 26.27 from one of
the bins at the entrance to the lecture hall!
Your last opportunities to get personal help before the midterm are
Wednesday, 1-2, Roe 168 (Colin problem session)
Wednesday, 2-3, Phy 107 (D
Announcements
Your last opportunities to get personal help before the midterm are
Friday, 3-4, Roe 055 (Colin review session)
Sunday, 5-6, Smartsite Chat Room (Colin office hour)
Monday, 11-12, Roe 164 (Paul office hour)
Good RC Circuit questions (stud
Gauss Law
MAIN POINTS
Use of Gauss Law to Determine Electric Fields
Spherical Symmetry
Gaussian surface is a sphere centered on the point of
symmetry.
Cylindrical Symmetry
Gaussian surface is a cylinder centered on the axis of
symmetry.
Planar Symmetry
Ga
Discussion 3 (these are two former exam questions!)
1. A very long, solid cylinder with radius has positive charge uniformly distributed throughout it, with
charge per unit volume . a) Find an expression relating the charge per unit length to the charge
p
Discussion 2 - Problem 21.90
Reading: Section 21.5, Problem-Solving Strategy 21.2, and Example 21.11
Part A:
1: Draw a picture of the charges and coordinate system in the space below. At this point, the picture should
be equivalent to Fig. 21.48 in the bo
CheckPoint: Forces on Two Charges
Electricity & Magnetism Lecture 1, Slide 1
CheckPoint: Compare Forces
+Q
Compare the magnitude of the net force on
q in the two cases.
1) |F1 | > |F2|
+Q
q
q
2) |F1 | = |F2|
3) |F1 |< |F2|
-Q
F1
4) Depends on sign of q
Ca
Continuous Charge Distributions
I don't understand the whole dq thing and lambda.
Summation becomes an integral (be careful with vector
nature)
Qi
E = k 2 ri
ri
i
dq
E = k 2 r
r
WHAT DOES THIS MEAN ?
Integrate over all charges (dq)
r is vector from dq to
Your Comments
I think the most difficult concept is the infinite line of charge. The x and y components are quite
confusing. I don't really understand what kind of effect does the x and y components has on the
electric field. I also mix up the F(force) an
Clicker Question: Balloons
Take two balloons and rub them
both with a piece of cloth.
After you rub them they will:
1) Attract each-other
2) Repel each-other
3) Either it depends on the material of the cloth
Electricity & Magnetism Lecture 1, Slide 1
Clic
Consider a charged rod of charge
and length . How do we find the
electric field at some point P a distance /2 away from the end of the rod?
P
2
Can we just use
where
and
?
Consider a charged rod of charge
and length . How do we find the
e
Answer Key
Phy 9C Quiz 1
Name: _
Student ID: _
1. Charged particles A, B and C are arranged on the corners of a rectangle, as shown in the diagram
below. If the net force on particle B is 45 degrees from vertical as shown, what is the charge
on
particle C
Phy 9C Quiz 3
Answer Key
Name: _
Student ID: _
1.
(5 pts) Consider a battery connected to a parallel-plate capacitor, as shown. The plates of the
capacitor are pulled apart while still connected to the battery. How do the following quantities
change (circ
Gary Gladding, Mats Selen, and Tim Stelzer
W.H. Freeman & Company
smartPhysics includes:
1. Online PreLectures (animated lessons, completed before lecture)
2. Online CheckPoints (quizzes to check knowledge, completed before lecture)
3. Online homework exe
Unit 1
MAIN POINTS
Coulombs Law
The direction of the force between two charges is always along the line connecting the
charges, and the magnitude is directly proportional to the product of the charges and
inversely proportional to the square of the distan
Unit 2
MAIN POINTS
Definition of Electric Field
The electric field at any point in space is defined as the total Coulomb
force exerted on a unit positive charge if it were fixed at that point.
&
&F
E
q
Electric Field Produced by a Distribution of Discrete