## 20121205

### Online reading assignment: heat transfers

Physics 205A, fall semester 2012
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 heat transfers.

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.
"How you can touch a Space Shuttle tile even when it has a ton of internal energy! I don't quite understand how so it is very interesting to me!"

"How a blackbody is really good at absorbing heat from light and is also a good radiator of heat, and a silverbody being the opposite."

"How Coffee JouliesTM cools down coffee yet keeps it warm longer."

"The windowpane problems really hit home with how much dual-pane windows conserve heat in the home (and mainly from the air gap)."
Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"I found much of this confusing because I have never dealt with it before."

"Fourier's law of conduction. Stefan's law of radiation. Wien's law."
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Still trying to grasp the reason why heat flows from hot to cold to reach thermal equilibrium." (This is merely a restatement of the zeroth law of thermodynamics--and this is something that is always observed to happen on its own in nature.)

"How is a kilocalorie the same as a calorie?" (A kilocalorie is a thousand calories. But a kilocalorie is equal to a Calorie (capitalized), also known as a 'food calorie.' No one wants to eat a 100,000 calorie candy bar (i.e., 100 kilocalories), but one would be more than willing to eat the same candy bar labeled as '100 Calories.'")

"What are Coffee JouliesTM?" (You can investigate how well a crude model of this device works in next week's laboratory.)

"Real-life example of a blackbody?" (Your car radiator, which is painted black in order to most effectively radiate heat, instead with of a light-colored or reflective surface.)

"I thought that if you had an 'A' in the class, you didn't have to take the Final Exam. Since we can earn 600/700 points (85.7%), and before the final 600 points are possible, shouldn't we be excused from the Final Exam if we have earned 514/575 points? That's more than 85.7% so far." (No. Your grade is determined by the total points, not by the average. This is so your grade cannot go down (as an average might), but can only go up (by accumulating more points). That's just how it is.)

"For the Final Exam will we need Scantrons?" (No, the Final Exam will be similar to the midterms (writing your answers on the exam itself), and will consist of four short-answer questions and three worked-out problems.)