Physics 110B

Physics 110B - Winter 2025

Lectures:	TR 11:00-12:15 Psych 1902
Discussions:	R 4:00-4:50 Phelps 1448
	R 5:00-5:50 Phelps 2514

http://hep.ucsb.edu/people/claudio/ph110b-w25

Announcements:

Jan 7: Physics Department Climate Document
Jan 7: To insure that I do not miss your emails, use the string [110b] at beginning of the subject line.
Feb 4: Information about the midterm

The midterm is on Tuesday February 11.
The midterm will cover the chapters in Griffiths covered up to and including those from the Week of February 3 (Tuesday's lecture only). (See Tentative Schedule at the bottom of the page)
You can bring two sheets of notes to the exam. You can write on both sides.
I will also distribute this formula cheat sheet with the problems.
For practice: last quarter's midterm is here. And here are the solutions. NOTE: the midterm had four problems, but students had to solve only three of them.

Here is the distribution of scores for last quarter's midterm.

It is likely that the midterm will also include a few quick multiple choice conceptual questions. TBD.
There will be a review session on Sunday February 9, 12 noon, Broida 1640. I will not prepare anythinf special, I will just be there to answer questions. So: bring your questions.

Teaching Assistant	Ziyue Wang
Instructor:	Claudio Campagnari
Email:	claudio@physics.ucsb.edu
Office:	Broida 5125. Phone 805-893-8802.
Office hours:	Thursday 12:30-1:30, or by appointment, or whenever you can find me.

Administrative Assistant:	Debbie Ceder
Email:	dla@physics.ucsb.edu
Office:	Broida 5014. Phone 805-893-2058.

Email:	zi-yue@ucsb.edu
Office hours:	Wednesday 3-5 pm

Learning Assistant	Filippo Delzanno
Email:	fdelzanno@umail.ucsb.edu
Office hours:	Tuesday 3-4 pm Wednesday 1-2 pm

Learning Assistant	Franklin Myhre
Email:	fmyhre@ucsb.edu
Office hours:	Tuesday 1-2 pm Thursday 1-2 pm

Graders	Ivy Li and Zhengyu Wan
Email	ili@ucsb.edu and zwan@ucsb.edu

Course Description:

Electrodynamics, Maxwells equations, conservation laws, electromagnetic waves, potentials and fields for moving charges, radiation, special relativity.

Textbook:

Introduction to Electrodynamics, Griffiths, 5th edition. Same as 110A (amazon link).
The 4th edition is also fine.
I will be (mostly?) assigning homework problems from the book (5th edition).
I need to know if there are students with the 4th edition, so that I can pick problems that are in both the 4th and 5th edition.

Additional Material

Wire size vs. current
In the January 16 lecture we talked about the fact that magnetic forces do no work on charges, because the magnetic force q v x B is perpendicular to the velocity and therefore perpendicular to the displacement. There are some interesting examples in Griffiths Chapter 8.3. In the Fall version of the class I went through the first of these examples (Example 8.5 page 380 in the 5th edition and described at the bottom of page 373 in the 4th edition). As I said in class, I had trouble understanding the technique he used to solve the problem. This quarter I have decided to skip this subject to save some time for later. But it is interesting, here is a writeup from last quarter that explains Griffith's method (it also shows an alternative derivation).
January 24: how to use Kirchoff's voltage law in a circuit.
January 29: About polarization of reflected and transmitted waves: here.
February 18: Alternative derivation of the Lienard-Wiechert potential: here.
February 23: Derivation of the fields from a charge moving at constant velocity ( Example 10.4 in Griffiths): here.
March 4: A note on Natural Units: here.

Homework:

Homeworks should be turned in via Gradescope. Code: TBD

Note: the number of interesting/good E&M problems that one come up with is somewhat limited.
If you search hard enough on the web, you are likely to be able to find solutions to many of the assigned problems (or
to very similar problems). Apparently, the latest version of ChatGPT can actually solve hard, graduate level, E&M problems (!).

My recommendation is that you try hard to do the problems yourself, or with your study group.
If you do end up getting help from the internet or other sources, make sure you understand the solution, do not
just copy it down. Maybe just take a hint to get started and then finish things by yourself.
To be clear: I am not encouraging you to do this, but I recognize reality, and I also think that there is some learning value
in looking things up, but only after you have made a good effort. Careful: do not overdo it! Remember that in the end you
will need to solve exam problems all by yourself.

In any case: if you get help with your homework from any source (internet, friends, study group...), make a note of
it with your solution. You will not be penalized in any way, but honesty is always good.

Homework Number	Due date	Problems	Solutions
1	Friday, January 17, 11:59 pm	here	here
2	Friday, January 24, 11:59 pm	here	here
3	Friday, January 31, 11:59 pm	here	here
4	Friday, February 7, 11:59 pm	here	here
5	Note non-standard due date Sunday, February 16, 11:59 pm	here	here
6	Friday, February 21, 11:59 pm	here	here
7	Friday, February 28, 11:59 pm	here	here
8	Friday March 7, 11:59 pm	here	here
9	Not due for grading. But strongly recommend you look at this homework to help preparing for the final	here	here

Discussion Session Materials
Attendance to discussion session is not mandatory.

	Date	Questions	Solutions
1	January 9	here	here
2	January 16	here	here
3	January 23	here	here
4	January 30	here	here
5	February 6	here	here
6	February 13	Review midterm questions	See below, in the Exams and Grading section, for solutions.
7	February 20	here	here
8	February 27	here	(Solutions are in the book)
9	March 6	here	here
10	March 13	Final from Fall 2024 Practice Final from Fall 2024	Solutions to F24 Final Solutions to F24 Practice Final

Exams and Grading:

There will be one midterm and one final.
The midterm will be on Tuesday, February 11 during normal class time.
The final will be Wedesday, March 19, 12-3 pm.

The final grade for this class will be calculated from a curve based on your scores on the Homework (15%), Midterm (35%), Final (50%).
For an example on how I previously arrived at the letter grades for a class, see this link.

If you miss the midterm for a good reason (eg: illness), your letter grade will be calculated based on the homework and final only.
If you miss the final you will be given an incomplete. You will take the Physics 110B final the next time that the class is being offered.
If, on the other hand, this is your last class that you need to graduate, we'll figure it out, somehow.

Midterm results
The midterm has been graded. You can pick up your graded blue book from Debbie Ceder, Broida 5014.
Here are the solutions (here is an addendum) Below is the score distribution.
scores

Tentative Schedule (TBD):

Sections from Griffiths

Week of Jan 6	7.1 7.2.1 7.2.2
Week of Jan 13	7.3.1 --> 7.3.5 8.1 8.3 (just the concept, see Additional Material entry)
Week of Jan 20	8.2.2 (skipping the ugly vector algebra) 8.2.3 9.1.1 9.1.2 9.2.1 9.2.2 9.2.3
Week of Jan 27	7.3.6 9.3 See also Additional Material entry dated January 29.
Week of Feb 3	Tuesday's Lecture: 9.4.1 9.4.2 Thursday's lecture: 9.5.1 9.5.2 (not finished, to be continued)
Week of Feb 10	Midterm week Finished 9.5.2, 10.1.1 10.1.2 10.1.3 10.2.1 (Started)
Week of Feb 17	10.2.1 (finished) 10.3.1 (but see my alternative derivation of the LW potential under Additional Material) 10.3.2 (skipped the algebra) Example 10.4 (see a complete derivation under Additional Material)
Week of Feb 24	11.1.1 11.1.2 11.1.3 (just the result) 11.1.4 11.2
Week of March 3	Review of other courses: 12.1.3 12.1.4(i) 12.2.1 12.2.2 12.2.3 12.2.4 More review (possibly): 12.3.1 12.3.2 12.3.3
Week of March 10	12.3.4 12.3.5 Problem 12.60