## 20130421

### Online reading assignment: generators

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 generators.

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.
"It was interesting to learn more about generators and how they create electricity, its just not what i had expected."

"I learned that the Space Shuttle tether generator is a single-use generator. I remember learning about this in high school, but I must've misunderstood, because I thought it was continuous generator revolving around Earth, rather than a single pass generator."

"I loved the video of the bike generator, because I ride a lot and do some spin classes. I always thought that attaching a generator to the wheel would be so cool."

"The continuous generators (Faraday disk, and rotating coil) were interesting because I had never seen them before, and wouldn't know how they work."

"The fact that you can touch an induction stove and not get burned, yet it can boil a pot full of water. We haven't gotten to the section that explains how this is possible, but I still find it fascinating!"

"A better understanding of motors. I knew you could flip them to make a generator, And I knew electromagnetic fields made them rotate."
Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"What the difference between an AC or DC generator was, how is the input/output reversed?"

"I was not aware of (or forgot about) single-pass generators. It is somewhat difficult for me to wrap my head around, as I always think of rotating things (continuous generators) with regards to generating electricity. What practical applications do single use generators have?"

"I am a little confused on how passing a rod through the middle of the magnetic field created by the moving emf makes the rod a battery."

"I thought a car starter could also act as a generator? I'll see you in office hours or something."

"I am still confused about differentiating voltage, amperes, current, energy, power, emf, etc. They all blur together in my mind."
Explain what a generator is supposed to "generate."
"A generator 'generates' electricity (turns the mechanical energy of motion into electricity)."

"Generators are suppose to generate current."

"They generate an emf."

"Power?"

"Everything a battery puts out."

"Volts or electrical potential difference."
Explain the meaning of "motional" in the term "motional emf."
"The 'motional' refers to a conductor actually moving through a magnetic field, or is in motion."

"I think that motional means that unlike a battery which is a chemical emf, the generators move to create the emf and current."

"MOVING."
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"≈:o" (See student comment below.)

"I think I might actually understand this section." (See student comment above.)