Physics 4: Introductory Physics
Electromagnetism and Optics
Syllabus
richman@charm.physics.ucsb.edu
http://hep.ucsb.edu/people/richman/richman.html
Welcome to Physics 4! What is your goal in
life? If it is to become an engineer or
to pursue a career in any of the sciences, this is an important class for you.
Technology depends heavily on the physics you will learn here. If you have some
other goals, you are still very welcome, but remember, this class isn’t
supposed to be easy!
My goal is to prepare people
heading towards an engineering or science career and help them to achieve their
ambitions. I will act as your guide to the challenging but rewarding world of
electromagnetic phenomena. This is hard stuff. Some of it is really
hard. This is going to be the real thing—I’m not going to water it down—because
if you are preparing for an engineering career, I want you to have a solid
foundation for acquiring the knowledge you need to compete and succeed.
I
have a second goal: to change the way you look at the world. The discoveries
and tools of physics are not only extremely practical, they can alter your
picture of physical reality, or at least enable you to appreciate it at a much
deeper level.
If
you take yourself and your own goals for the future seriously, this will be a
good class for you. This is not a good class for people who are not serious about
learning or who are pretending to do something that they are not actually
doing.
To
succeed in learning this subject, you need to do three things:
I
cannot guess all of your questions. Unless you get up the courage to ask them,
you risk being permanently stuck on some point that you will need to know not
only to understand the present material, but possibly for a lot of material to
come. To summarize: questions in class (or office hours) are strongly
encouraged!
The
material in Physics 4 makes extensive use of material you have covered
in Physics 1, 2, and 3. Physics is quite unforgiving in this respect, because
it builds heavily on previous material. You cannot just say, “now that we are
on Chapter 27, I can forget about Chapter 24.” Quite the opposite. Especially
in Physics 4, where we study the joint behavior of magnetic and electric
fields, you need to know a very large amount of material from previous chapters
on electric fields (chapters 21—26), as well as a lot of stuff from earlier
chapters.
You also need to be expert
in the use of vectors. If you find vectors confusing or difficult, you will have major
problems in Physics 4. If you are in this situation, please talk to me as soon
as possible. I recommend that you do all the problems in Chapter 1. You don’t
have time to spare. If you cannot use vectors, you will not be able to pass
Physics 4.
Students
with an engineering orientation sometimes take the following attitude towards
physics classes: “I understand that I have to learn this stuff, and I know it’s
important. But all I really need to know is which formulas to memorize; then
I’ll just plug numbers in and get the answer.”
Unfortunately, this approach often leads to much sadness and despair. In
this minimalist version of understanding physics, several things commonly go
wrong:
Physics
problems (and real-life engineering problems) are usually not suited to the
“plug-and-chug” approach. The information provided does not neatly match all
the variables required to evaluate a certain formula from the chapter. Often,
information is presented in a way that requires you to apply some simple
geometrical relations in order to use it. Students who tend to forget things
like the area of a circle have additional hurdles because to them, the problem
contains an additional “problem” that should really only be a trivial one.
Here’s
an example: in one problem, students needed to calculate the electric current
(I) in a certain situation. In the problem, there were no resistors or voltages
given, but the students really, really wanted to use the formula I = V/R. Many
students were stuck for hours. To calculate the current, all they needed to do
was go back to its fundamental definition, I=dQ/dt. But the students could not
focus enough on the physical situation enough to realize that Ohm’s Law was not
even applicable. (They had also forgotten the definition of current.)
So
here is some advice. Physics is a lot more fun when it isn’t just a bunch of
formulas with abstract symbols. And anyway, as engineers, you need to
understand the formulas at a deeper level, otherwise you won’t know whether
they are applicable to the problem you are trying to solve. When you are
working a physics problem, try the following procedure:
Prof.
Richman’s tried and true recipe for solving physics problems
You
might think this list is too much. It isn’t. It’s exactly what you need to do. This
process will save you time in the end. If you are building a bridge, designing a new
cell phone, creating new diagnostic instrumentation for a hospital, or
inventing a new process, you will be committing resources of your company. Carefulness
and correct results will be rewarded (and vice versa). Good luck!
Class |
Date |
Topics |
Chapters
|
1 |
Mon,
Jan 9 |
Introduction, review of Ph 1-3 |
27 |
2 |
Weds,
Jan 11 |
Magnetic field & magnetic forces |
27 |
3 |
Fri,
Jan 13 |
Magnetic field & magnetic forces |
27 |
- |
Mon,
Jan 16 |
MLK
|
|
4 |
Weds,
Jan 18 |
Magnetic field & magnetic
forces
|
27 |
5 |
Fri,
Jan 20 |
Sources of magnetic field |
28 |
6 |
Mon,
Jan 23 |
Sources of magnetic field |
28 |
7 |
Weds,
Jan 25 |
Sources of magnetic field |
28 |
8 |
Fri, Jan 27 |
Electromagnetic induction (HARD!) |
29 |
9 |
Mon,
Jan 30 |
Electromagnetic induction (HARD!) |
29 |
10 |
Weds,
Feb 1 |
Electromagnetic induction (HARD!) |
29 |
11 |
Fri,
Feb 3 |
Inductance
|
30 |
12 |
Mon,
Feb 6 |
Electromagnetic
waves (HARD!)
|
32 |
13 |
Weds,
Feb 8 |
Electromagnetic waves (HARD!) |
32 |
14 |
Fri, Feb 10 |
MIDTERM
|
Chapters 27-30 |
15 |
Mon,
Feb 13 |
Electromagnetic waves
(HARD!) |
32 |
16 |
Weds,
Feb 15 |
Nature and propagation of light |
33 |
17 |
Fri, Feb 17 |
Nature and propagation of light |
33 |
- |
Mon,
Feb 20 |
Presidents’
Day |
|
18 |
Weds,
Feb 22 |
Nature and propagation of light |
33 |
19 |
Fri,
Feb 24 |
Geometrical optics |
34 |
20 |
Mon,
Feb 27 |
Geometrical optics |
34 |
21 |
Weds,
Mar 1 |
Geometrical optics |
34 |
22 |
Fri,
Mar 3 |
Geometrical optics |
34 |
23 |
Mon,
Mar 6 |
Interference |
35 |
24 |
Weds,
Mar 8 |
Interference |
35 |
25 |
Fri,
Mar 10 |
Interference/Diffraction |
35/36 |
26 |
Mon,
Mar 13 |
Diffraction |
36 |
27 |
Weds,
Mar 15 |
Diffraction |
36 |
28 |
Fri,
Mar 17 |
Review |
|
FINAL |
Fri,
Mar 24 |
FINAL EXAM |
Covers
textbook, HW, lectures, demonstrations |
Grades,
homework, tests, and all that stuff
·
Homework (online) will be assigned on
Thursday and is due on the following Thursday night. A penalty will be applied
to late homework.
·
Lectures: Mon, Weds, Fri from
·
Lab Sections—see the Schedule of Classes
·
Graduate Teaching Assistants: TBN
·
Professor Richman’s office hours: Weds
·
Grading policy:
1.
MasteringPhysics Homework: 15%
2.
Quizzes (not Quiz 0) + Class Participation
(clickers): 20%
3.
Midterm: 15%
4.
Final exam: 50%
·
Textbook: University Physics, by H.D. Young and R.A. Freedman, 11th
Edition
·
Final Exam Date: see schedule below.
·
The quizzes will be on Fridays (some, not
all) and will cover material from the homework, lectures (including the
demonstrations!), and text. Not all of the quiz problems will be numerical;
some will be “conceptual.”
·
You will use the MasteringPhysics online
system (http://www.masteringphysics.com)
to submit your answers to homework problems. You should be familiar with this
system from Physics 3. The Course ID to use when registering on
MasteringPhysics is MPRICHMANW06.
·
Homework solutions will be posted on ERES
(http://eres.library.ucsb.edu/).
·
Laboratory sections: you must register
separately for Physics 4L and buy a lab manual from the bookstore. Grades from
Physics 4L are determined separately from those for Physics 4. The lab (Physics 4L) is treated almost as a
separate course, with independent grading and policies. Please consult your lab
T.A. for information.
·
Cheating in any form is
not acceptable and will result in severe consequences. If you have any
questions about this, please come and talk to me.
The
Importance of Electromagnetism
The
unification of two seemingly different forces, the electric force and the
magnetic force, is one of the great achievements in science. This unification
is expressed in Maxwell's equations, which we will develop this quarter. The range
of phenomena that these equations describe is truly vast, and we will explore a
wide variety of fascinating examples.
For
engineers, there are countless technologies that exploit the properties of the
electromagnetic field and the ways in which this field interacts with matter.
Communications, computing, and many energy technologies depend critically on
our understanding of electromagnetism. If you are preparing for a career in
engineering, the understanding of electromagnetic phenomena is one of your most
important tasks.
Maxwell's
equations came about through the efforts of many people, and after much
experimentation, but the full set of equations was finally synthesized by
Maxwell around the time of the U.S. Civil War. The famous physicist Richard
Feynman wrote (Feynman Lectures on Physics, Vol. II, p. 1-11) that when
historians 10,000 years from now look back at the events of the 1800s, the
Civil War will pale in significance compared with the discovery of Maxwell's
equations. It is certainly true that our ability to control and exploit the
electromagnetic field has had profound implications for human history. Consider
just a few examples: the electric light bulb, radio communications, radar, the
television, medical imaging with X-rays and nuclear magnetic resonance,
electronic circuits, fiber optics, lasers, the computer, magnetic and optical
storage disks, and the cell phone. Each of these and countless other
innovations affect our daily lives.
One
of the most intriguing and useful aspects of electromagnetism is the existence
of electromagnetic waves. In such waves, the electric and magnetic fields
interact with each other in a way that sustains and propagates the wave. We
will be able to infer the existence of such waves from Maxwell's equations.
Although visible light is just a narrow sliver of the electromagnetic spectrum,
it is a very important sliver to us! Each of us owns two extremely powerful
visible-light optical systems: our eyes. But other parts of the spectrum, from
gamma rays and X-rays to infrared light, microwaves, and radio waves also play
a huge role in science and technology.
Maxwell's
equations underlie all classical phenomena involving electric and magnetic
forces. The term classical is often used in physics to mean that we are
not including quantum phenomena. We will, however, discuss some of the
limitations of Maxwell's equations so that you understand their range of
applicability. In particular, if you investigate the behavior of
electromagnetic fields at very low intensities, you would discover that
electromagnetic energy cannot be manipulated in arbitrary amounts. The
excitations of the electromagnetic field occur in discrete quanta, called
photons.
For many, many processes of interest, we do
not notice this "graininess" of the electromagnetic field, but for
other processes it is absolutely crucial. If you want to continue with physics
and go on to study quantum phenomena involving electromagnetism, you will
certainly need to know Maxwell's equations to serve as the starting point.
One
interesting feature of Maxwell's equations is that they are fully compatible
with Einstein's special theory of relativity. In Einstein's theory, the speed
of light is a constant, as long as the light is propagating in vacuum. At first
this might seem obvious, but it is quite surprising, even shocking, when you
realize that regardless of the velocity of the observer, the speed of light is
the same. Even if you "chase" the light coming from a flashlight, the
speed of the wave with respect to you does not change! This conclusion, which
is fully supported by experiment, means that space and time are inextricably
linked.
Another
aspect of Maxwell's equations is that if one reference frame is moving with
respect to another, the observers in these two frames see different electric
and magnetic fields. One person's electric field is another person's magnetic
field! We will touch on this point briefly, but you will need to take an
upper-division class on electromagnetism to fully explore this phenomenon.
Objectives
for this Class
The schedule at the
end of this syllabus gives you a lecture-by-lecture plan of the material we
will cover in this course. Below I list some of the main concepts you will need
to master. I don't list every one here, just the main ideas.
1.
The effect of
magnetic fields on charged particles and on objects containing charged
particles. In other words, if a magnetic field is present, what is the response
of a system to this field? The response of magnetic dipoles is extremely
important, because (as far as we know) there are no magnetic monopoles, so
dipoles are the simplest system we can treat (C27).
2.
How to produce static (constant in time)
magnetic fields. In physics, we use the term "sources" to indicate
something that can produce a certain type of field. Interestingly, the sources
of magnetic fields come in two characteristic types: (1) electric charges in
motion (either individually or as currents) and (2) electric charges that are
spinning. Most elementary particles, such as electrons and protons, have an
intrinsic, quantum-mechanical spin, so they generate magnetic fields
automatically (C28). This explains how we can have substances like iron, which
generate magnetic fields without an obvious source of electric current.
3.
How a
time-changing magnetic field produces an electric field. How a time-changing
electric field produces a magnetic field. (These are called induced fields.)
Synthesis of these and other results into Maxwell's equations (C29).
4.
How energy is
stored in magnetic fields and how we characterize this using the quantity of
inductance (C30).
5.
Analysis of
circuits with R, L, and C circuit elements (C30, C31). These topics will be
covered mainly in lab.
6.
How propagating
and standing electromagnetic waves arise from the interplay of time-varying
electric and magnetic fields. Properties of electromagnetic waves (C32).
7.
Phenomena
involving light: reflection, refraction, dispersion, polarization, other wave
effects (C33).
8.
Geometric
optics and optical instruments. Practical applications (C34).
9.
Interference
effects arising from the linear superposition of electromagnetic waves (C35). Diffraction (C36) is also a superposition
effect closely related to interference.
More
General Advice
Electromagnetism is a difficult subject, with
many abstract concepts and some complicated mathematics. Here are some specific
suggestions on how to do well in Ph 4:
1.
As for nearly all physics classes, the single most important thing is to do
the problem sets as well and as carefully as you can. It is amazing how
many mistakes can be avoided and how much time can be saved by simply writing
neatly! You will often need to "debug" your homework solutions, much
as you would debug a computer program. Well organized and carefully written solutions
will be much easier for you to debug than a sloppy mess. They will also help
you study for the quizzes and the final!
2.
Special comment about MasteringPhysics.
The online MasteringPhysics system is reasonably good, but it can have its
frustrations. Print out the MP
assignment and work on it away from the computer, writing out complete
solutions before attempting enter your answer. If you come to me in my
office for help on a homework problem, the first thing I will do is ask to see
your work.
3.
You should review your old problem sets
from time to time to check that you have assimilated the material.
4.
Prepare ahead for the lectures.
Read the chapter before I present the material in lecture. Why? The book is
available to you all the time. The lecture happens only once. To get the most
out of it, you should already have some familiarity with the material.
5.
Remember
things. Many physics students are disinclined to
remember important results, thinking that these can always be derived or looked
up whenever necessary. However, if you remember things, it will greatly
facilitate both learning new material and solving problems: the amount of “new”
material will seem less, because you will be more familiar with the old
material used in the derivations.
6.
Given the difficulty of the subject, it
is important to work especially hard to keep up. In studying my lectures or the
text, you will generally need to go over the material several times. Reading the text or your notes is not
enough. You have to actively carry
through the derivations and analyses on your own. Some students simply try
to read the same thing over and over again, and then discover that they aren’t
learning any more by doing so. A better approach is to read through the
material once or twice and then try to derive
the results on your own, referring to the text only if you are stuck. If
you don’t understand a particular aspect of the analysis, note this down and
continue. Then, bring your list of questions to class, discussion section, or
office hours.
7.
Be
an active listener and a participant in lectures. It
is essential to make the best use of your time in lecture. This means really
paying attention, taking good notes, and asking good questions. But don’t just
be a note-taker! Questions from students are usually incredibly helpful to
everyone—professor and other students—by helping the professor to clarify
confusing points and to make sure that the most important information does not
get lost in the details. Often, the best students are the ones who ask questions,
since others feel that they do not know enough to ask one. I strongly encourage
you to ask questions even if they are not perfectly formulated!
8.
You
are encouraged to find other books on electromagnetism—there
is a vast number—to find alternative presentations, examples, and problems. The
Feynman Lecture on Physics are great.
Don’t let the class set the boundary for
your learning. There is no boundary!
More Advice for Physics 4 and for ALL of
LIFE
Many
of the skills and habits that will increase your success as a student are
exactly the same ones that will help you to be successful as an engineer.
Always show up, pay full attention and be
as disciplined as possible. In the university, showing up means
coming to every class, just as engineers must always show up to work on
time and to meetings in their companies.
In the real world, you will be expected to
absorb and to use information rapidly. Learning to pay full attention in
class is very good practice. Why do students sometimes come to class and not
listen? I don't know.
Engineers need to deliver results in the real
world on schedule and on budget. Companies require their engineers to deliver
products, designs, and ideas. Engineers are expected to perform at a very high
level in their companies---or else the company will find someone else to do the
job. In a company, you would not dare to hand in sloppy work. Develop a
professional style and professional habits now.
Learn
to plan and to develop strong organizational skills. They will not only help
you now, they will be essential in your future jobs. Use self-discipline in
implementing your plans. CAREFUL PLANNING WORKS if you stick to
your plans.
Now is the time to invest in your own future.
The world is a very competitive place. Prepare for it by setting high goals and
high standards for yourself.