“The value of an education… is not the learning of many facts, but the training of the mind to think something that cannot be learned from textbooks.” – Einstein
Courses taught
I have taught several undergraduate physics courses at Cornell as a Teaching Assistant, as detailed below in reverse chronological order:
 PHYS 3327: Advanced Electricity and Magnetism, Fall 2016
Course instructor: Prof. Itai Cohen [course website]
Instructed discussion section, taught Mathematica, designed numerical problems
Student evaluations: find here  PHYS 2216: Introduction to Special Relativity, Fall 2016
Course instructor: Prof. Michelle Wang
Designed iClicker questions and exam problems, graded  PHYS 1116: Mechanics and Special Relativity, Spring 2016
Course instructor: Prof. Michael Niemack
Instructed discussion and lab sections, prepared quizzes, graded
Student evaluations: find here  PHYS 2213: Electromagnetism, Fall 2015
Course instructor: Prof. Kyle Shen
Instructed two discussion and one lab sections, managed discussion forum on Piazza, created new demos with Jenny Wurster, graded
Student evaluations: find here  PHYS 1203: Physics of the Heavens and the Earth, Spring 2015
Course instructor: Prof. David A. Kronreich
Instructed discussion section, graded
Student evaluations: find here  PHYS 2208: Fundamentals of Physics II, Spring 2014 and Spring 2013
Course instructor: Prof. Matthias Liepe
Instructed three discussion sections, prepared quizzes, graded
Student evaluations for Spring 2014: find here
Student evaluations for Spring 2013: find here  PHYS 2207: Fundamentals of Physics I, Fall 2012
Course instructor: Dr. Kathy Selby
Instructed two discussion and one lab sections, prepared quizzes, graded
Student evaluations: find here
Ideas about teaching (physics)
I love teaching – its a challenging and rewarding exercise. My ideas about teaching keep evolving, but here are some of the things I have learned thus far and try to follow:
 To be a good teacher, one needs to be enthusiastic about the subject oneself and be able to share some of that excitement with the students (think Feynman!), in a way which makes them think and ask questions.
 It takes time! Learning how to teach is a process of trial and error and requires a lot of effort. Similarly, students need time to absorb what they are being taught. Too often teachers and students are in a hurry to “get things done” which compromises learning.
 Its important to empathize with the students and keep in mind that they come from different backgrounds. One should strive to adapt one’s method of teaching to cater to all such backgrounds, though it is difficult to achieve in a large class.
 Most of us learn physics (or science in general) by seeing, thinking, and doing. Therefore one should try to promote these activities, e.g., by designing puzzles and conceptual exercises, showing demos, holding open discussion forums etc.
 Students often come with preconceived ideas, or there is a disconnect between what they believe and what they know “should” be the answer (think Newton’s 3rd law!). Thus it is sometimes useful to follow a wrong assumption to its conclusion to show why it doesn’t work, rather than simply giving the right answer.
 Teaching should be a dialogue between the teacher and the students. Thus the teacher should have an open mind and be willing to learn from the students. I often learn new ways of thinking about a problem from interacting with students.
 Its good to keep reinventing. Whenever I teach a course, I like to come up with new exercises which illustrate a concept (you’ll find some examples below). Not only is the process enjoyable, but I invariably also learn something new about the subject myself.
 Student feedbacks are important – not only at the end of a course, but on a regular basis throughout the course – for better learning and improving as a teacher.
 Teaching outcomes can be measured and should be studied scientifically. Indeed, physics education research has developed into a field of its own and is shedding light on what works and what doesn’t, such as the use of flipped classrooms, and the benefits and drawbacks of testing. Even if one is not involved in such studies, one should be aware of the findings and incorporate them as much as possible.
It also helps that at Cornell there is a strong community dedicated to improving education, which gives me a chance to participate in projects such as the Active Learning Initiative, PER journal clubs, and events organized by the Center for Teaching Innovation.
Resources
Here you will find a collection of exercise problems, animations, and notes I prepared – those which I had reason to write up and save for posterity. Feel free to use them. You will find external links to more resources on the Links page.
Exercise problems
The problems (click for pdf) were largely motivated by my interactions with students who asked some very intriguing questions! They are also influenced by the books that I read.
 Conceptual problems on Special Relativity: These were designed to be clicker questions in an intro course on special relativity. Their goal is to illustrate that not everything is relative and that the bizarre predictions of the theory, such as time dilation, length contraction, and relativity of simultaneity, are all necessary for logical consistency. The problems were greatly inspired by two excellent thoughtprovoking books by Prof. David Mermin: Space and Time in Special Relativity and Its About Time, two of the best expositions I have read on the logical coherence of Special Relativity.
 Numerical problems on Electromagnetism: These were used as homework problems in an advanced E&M course for undergraduate physics majors. They are more focused on gaining insight into electromagnetism than on numerics. They were designed for beginners in Mathematica, but other programming languages should also work fine.

In addition, we worked on numerical problems in sections. The sections consisted of both learning Mathematica and using it to investigate problems which cannot be solved analytically. Those exercises are summarized in Mathematica (version 11) notebooks which you can download as a zip file (6.6 MB).
 Mechanics problems: These were used in quizzes given to freshman physics majors.
 Quiz problems on Electromagnetism: These were used in a course for premeds.
Cool animations
 We are taught in electrostatics that all free charges reside on the surface on a conductor. But (how) do they always reach such a configuration? Turns out there are two crucial factors – find out in these simulations: [pptx (4.5 MB)] [key (5 MB)]

In particular, they can selforganize into beautiful patterns!
 Imagine a charged pendulum in a vertical magnetic field. Depending on the field strength and how you release the pendulum, it can undergo different types of oscillations, forming beautiful trajectories. See for yourself in this interactive simulation: zip file (can be played in Mathematica or the free CDF Player).
 As seen from Earth, Mars and other planets move backwards every once in a while. This retrograde motion puzzled ancient astronomers until the time of Copernicus. You can see how this apparent motion emerges in this interactive simulation: zip file
(can be played in Mathematica or the free CDF Player).