Online reading assignment: capacitors

Physics 205B, spring semester 2013
Cuesta College, San Luis Obispo, CA

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing presentations on capacitors.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.

"I thought it was interesting that a capacitor's potential energy can be used for a cardiac defibrillator."

"I am interesting in asking more about electronics. I will stop by office hours to ask."

"I think that it is interesting that we are going over material that everyone can easily relate to."

"I was interested by the KIRF (keeping it real fake) capacitors. It made me laugh knowing that to make more money, people will definitely cheat you."

"I liked the explantation of why field lines point towards decreasing electric potential values. I didn't quite get why before, but now writing out the math makes it all make sense."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.

"Formulas. How do people come up with these equations?"

"The difference between capacitors and capacitance."

"Understanding why capacitors are necessary is still not clear to me. What happens to if you simply remove a capacitor in a circuit that needs one?"

Explain why increasing or decreasing the voltage (electric potential difference) of a capacitor cannot change the numerical value of its capacitance.

"Voltage cannot change the numerical value of the capacitance because once the capacitor is built, that number is a fixed value and only reconstruction will change that number."

"Because its capacitance is based on the d between plates and the size A of those plates."

"I'm not sure what this is asking."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"Is this possible?" (Yes. At 01:25, note that the hose is shaking up and down; such that the water stream would be wiggling up and down as well. The trick here is that the video frame rate is (nearly) synchronized to the hose and water stream oscillation, such that you are only seeing the water stream each time it returns back to the same position once per cycle, making it look stationary.)

"I'm scared for the quiz tomorrow and the midterm." (Feeling fear is normal. It means you're alive. And more importantly, motivated to study.)

"Electricity confuses me!" (Trying to figure how to teach electricity confuses me, too. Somehow we'll get through this, both you and me.)