20140331

Online reading assignment: advanced electricity

Physics 205B, spring semester 2014
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 advanced electricity concepts.

Selected/edited responses are given below.

Describe what you understand from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically demonstrate your level of understanding.
"Even though wires have a low resistance, a large enough current can overheat and melt the wire. Circuit breakers combat that by cutting off the current if it gets too large."

"An ammeter needs to be wired differently than a voltmeter. 'Twinkle twinkle little star, power equals i squared r.'"

"Power is the rate energy conversion takes place and is the product of current and potential difference. A voltmeter measures the potential difference across the resistor. An ammeter measures the current through the resistor. Both voltmeter and ammeter are used to measure the resistance in a circuit."

"Ammeters, are placed within the circuit and approach zero resistance. Voltmeters are placed on a circuit and approach infinite resistance (so that they don't operate as an in parallel conduit). Household circuits have all of their plugs wired in parallel, with more resistors in parallel, more current in drawn leading to potential overheating, thus requiring a circuit breaker to guard against this."

"The power dissipation equations do look very familiar to the potential energy equations. It makes a little more sense why households have parallel rather than series wiring because the voltage will be same throughout."

"An ammeter breaks into a circuit, whereas a voltmeter feels the current running through the circuit. In this class, we'll consider resistance to be unaffected by temperature."

"I understand that the voltmeter measures the change in voltage so it must be connected before and after the current flows through a resistor. I also understand that the current increases when more parallel resistors are added."

"Even though wires have a low resistance, a large enough current can overheat and melt the wire. Circuit breakers combat that by cutting off the current if it gets too large."

Describe what you found confusing from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically identify the concept(s) that you do not understand.
"Not quite sure about the difference between an ammeter and voltmeter."

"What I find confusing is the new material. I understand that a multimeter can be used as a ammeter (current) and voltmeter (change in electric potential), but I am having a hard time understanding the 'break-in' connection for the ammeter set up. I am also having a hard time putting all the different concepts together to understand power dissipation. I am not sure when and how to use all the different equations."

"There are lots of equations to interpret."

"I didn't find anything to be too confusing that I couldn't figure out on my own going through the presentations and the section in the book once more."

"I'm not really following what the power dissipation stuff is. I'm not seeing how it is specifically used in the types of problems we've been doing."

"I don't understand how power dissipation is applied to a situation."

"I'm a little confused in the blog presentation about the joule heating. What is actually going on there and why is that significant to currents."

"I'm still not feeling great about what all the variables represent in these equations. Current, voltage, electric potential energy, etc."

"I didn't really understand the concept of joule heating. Is it just the same thing as electrical power?"

"I don't understand how power relates to everything yet a brief overview in class would be great. How does power relate to current voltage and resistance conceptually, the equations are okay."

"I'm confused about the junction rule and the loop rule. I understand as far as looking at them in a series or parallel but I don't understand WHEN to apply them. Seems like one deals with current and the other voltage."

I'm just slightly confused about when to use a certain power equation. If there is a rise in electric potential, should the preferred equation be the one where the potential difference is squared?"

"Rises and drops in emf, the loop rule, and the junction rule are coming to me like sludge moving upwards through a pipe. More explanations this Monday would be very much in order."

State the unit of electrical power, and give an equivalent definition in terms of other SI units.
"The watt (symbol: W). The unit, defined as one joule per second, measures the rate of energy conversion or transfer."

"Amps?"

"J = N·m?"

What are the resistances of these (ideal) devices?
(Only correct responses shown.)
Ideal ammeter: 0 [88%]
Ideal voltmeter: ∞ [81%]

Plugging in and using additional electrical appliances in the same household circuit would increase the total __________ in the wiring inside the house.
current.  *********************** [23]
voltage.  *** [3]
(Both of the above choices.)  ** [2]
(Neither of the above choices.)  ** [2]
(Unsure/guessing/lost/help!)  ** [2]

A fuse or circuit breaker is designed to prevent too much __________ in household wiring.
current.  ******************************* [31]
voltage.  [0]
(Both of the above choices.)  [0]
(Neither of the above choices.)  [0]
(Unsure/guessing/lost/help!)  * [1]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Can we please go over power dissipation and how to use the equations? (And generally go over all the new material.)"

"I'm still not confident with the more complex circuit problems and how you can find each value after you solve for the total circuit current."

"The midterm wasn't too hard."

"I don't have any questions right now."

20140330

Online reading assignment question: keep, quit, start

Astronomy 210, spring semester 2014
Cuesta College, San Luis Obispo, CA

"140330-Astr210-keep"
http://flic.kr/p/mB7ufF
Originally uploaded by Waifer X

Wordle.net tag cloud for "keep" resolutions generated by responses from Astronomy 210 students at Cuesta College, San Luis Obispo, CA, spring semester 2014 (www.wordle.net/show/wrdl/7702236/Untitled).


"140330-Astr210-quit"
http://flic.kr/p/mB9aaS
Originally uploaded by Waifer X

Wordle.net tag cloud for "quit" resolutions generated by responses from Astronomy 210 students at Cuesta College, San Luis Obispo, CA, spring semester 2014 (www.wordle.net/show/wrdl/7702233/Untitled).


"140330-Astr210-start"
http://flic.kr/p/mB9a6o
Originally uploaded by Waifer X

Wordle.net tag cloud for "start" resolutions generated by responses from Astronomy 210 students at Cuesta College, San Luis Obispo, CA, spring semester 2014 (www.wordle.net/show/wrdl/7702232/Untitled).

Students were asked to answer a "keep-quit-start" online reflection (hosted by SurveyMonkey.com) on their studying strategies/pitfalls (Mubayiwa, 2009).
Enter a word or brief phrase that describes what you intend to keep doing to study for this class. Explain your answer to the above question (what you intend to keep doing to study for this class).

Enter a word or brief phrase that describes what you intend to
quit doing to study for this class. Explain your answer to the above question (what you intend to quit doing to study for this class).

Enter a word or brief phrase that describes what you intend to
start doing to study for this class. Explain your answer to the above question (what you intend to start doing to study for this class).
[Word tags have been edited to consolidate related common subjects; student explanations are verbatim.]

Keep word tags:
caring
      I really do care about my grade in this class. And i actually find it interesting, so I plan on to keep caring about the material covered in class.

everything
      Continue to read my assigned chapters, show up to class, and study for my quizzes.

flashcard questions ("peer-instruction," "think-pair-share")
      I have gotten very high scores on every quiz and test in this class because I have used the flashcard questions for each quiz to study. These questions help me to focus on what I need to know instead of overwhelming myself with too much of the hefty information. Since I have received such good results from studying these, I plan to continue to do so.
      Not only am I determined to keep doing this but doing it more. I've already started to study for upcoming quizzes by printing out the flashcards which I've only done twice before. Other quizzes I just studied my notes and the flashcards are a definite help, I just never give myself enough time to finish all the questions, so take more time for them is my plan.
      Flashcards have really helped me because that forces me to actually find the answers by myself. I also really like how we can send you our answers, and the ones we got wrong you help explain them to us.
      The FCQ help me alot in studying and preparing for the tests.
      Reviewing the flashcard questions helps gear me towards what i need more review on an what I'm okay with. The in class activities help solidify information and work out any kinks utilizing peers.
      I have recently found it very helpful to print the flash card questions so that i can keep notes while participating in class. These flashcard questions are a great way to study for the quizes and i feel more prepared when i am actively working on them.

focus
      The answer is simple, my goal is a 4.0 gpa this semester and so my goal in this class is an A. In order to do that I must remind myself of the bigger picture of getting a 4.0 gpa and by staying focused on that it will help me succeed in this class and others.

go to class
      There really should be no reason for Me to miss class, so I'll show up when iI'm supposed to and participate in every lecture.
      So much material is presented in lectures that is present on the tests and necessary to really understand concepts as a whole, rather than as vocabulary terms. Without going to class I don't see how someone could ever get a grasp on what we're learning.
      I feel that showing up to class helps the most, as it should. All the slide shows and lectures, in-class assignments, flash card questions all help a lot more than anything I could do at home.
      This is where I do the majority of my learning in the class, and it is also what keeps the material in my mind the best. I do not learn from simply reading, I need to do it, and this provides a perfect solution to my problem.
      I am going to study harder so i can succeed on my quizzes and make sure that I'm not only doing the in class assignments but understanding them as well.
      I to keep coming to class. Considering this class is only 1 night a week, I am going to try to never miss it because we do cover so much information during once class.
      I intend to continue going to each class, study, and ask the questions I have.
      I intend to keep attending class and paying attention to whats going on. I actually retain information that way. I need to print off the group assignments so i can fill out a copy to keep it with me to study from.
      I definitely learn the material best in class, it's much easier to understand it when you explain it and we do the activities than just doing the reading.

homework
      The reading homework and presentations seem to be the foundation for the class.
      I have not performed the absolute best I can on certain past quizzes and at times forgot to complete the online reading assignments. I have made sure to improve at these things the last couple weeks and intend to KEEP doing these things to become even more successful in the second half of the course than the first.
      I'm usually pretty good at completing the weekly reading assignments and plan on keeping that up in order to keep earning points.
      i intend to complete every pre-read and prefab on time before every class.

observations
      I've noticed lately whilst taking this class that I've taken note of the moon and its stages much more frequently while outside of class than I ever have before. It helps me get into an astronomical mind set which helps me study.

pay attention
      This class is one where you have to keep your ears open. Keep on the studying and converse with your fellow classmates.
      While I'm in class, I try to devote my full attention to the task at hand so I will understand when the test comes around.
      This class is all about the in class activities and being prepared for them. As long as I keep reading and being prepared for class, I will get an A.
      I normally listen pretty well but there are times when it goes in one ear and out the other, so hopefully if I keep paying attention and listen, I'll do better in this class.
      I consist focus on the topic on hand which is helpful in group activities

practice exams
      I intend to continue doing the practice quizzes to prepare for quizzes, midterms, and the final.

reading
      Reading the text and taking notes from the textbook, is really valuable to my success because once I have taken the notes I can go back and study them.
      Re-read the text and review material often.
      I can KEEP doing my homework by reading the chapters and going over the presentations that we do in class.

review
      I am a diligent student who is pretty well able to manage my time and energy. I consistently go over material discussed in class, in addition to printing up in-class assignments i need more review of and make it a point of printing and completing all of the various quiz flashcard questions. Plus, i genuinely want to do well.

study group
      I have been working with a group of people from the class on studying and a lot of it is me answering questions they have about astronomy. For the most part I can answer the questions and explain it to them so they understand. This helps me learn and helps them learn and I think thats been the most helpful in succeeding in this class.

studying
      I have studied a lot so I feel I know the material and my quiz score backs that up so I intend to continue doing that and asking questions really trying to understand concepts.
      Study my material more carefully as I do not have the right book, and it took me awhile to adjust to the online parts of the course.
      I am not such a smart person that I get good grades without studying the material. It is the time that I spend outside of class reinforcing the knowledge that helps me succeed the most! In order to get a lot out of a class, I have to put all the necessary time into studying the material.
      Need to keep knowing the material sufficiently to score well on those things!
      So mastering the material for me means, keep reading all the presentations, assigned reading and do all the pre-lecture material. Don't just go through the motions, really try and absorb what is being taught so I can be ready to answer essay questions.
      i need to study a bit harder to earn the score i want.

take notes
      I use my notes a lot to study for quizzes and tests so i'm going to keep taking notes in class because it helps me understand things later when i'm not in class.
      I have been going over the presentations and notes I take during class discussion, and it has been helping me to succeed in this class.
Quit word tags:
cramming
      I know everyone has busy schuldues but if I looked over the reading once a night before I went to bed I would not have to study as hard when I cram it all into one night.

daydreaming
      I have a hard time paying attention in class because I randomly drift off somewhere SOMETIMES. So I hope to get out of that random habit and focus more.

multitasking
      I can QUIT multi- tasking and focus on each class and pay attention so I know the subjects more. Pay attention and ask questions when needed so I know the correct answers.

my job
      i recently was working 40 hours a week and i couldn't keep up with my school work, so i quit my job and found a new more accommodating one.

not asking questions
      When I don't understand a topic I tend to not ask for help, and try to figure it out for myself-which usually doesn't work. I'm going to quit doing this.

not reading
      Even though I do not learn the best from simply reading, it is still important to get the foundation of the lesson to build up on it. I cannot simply make something out of nothing.

procrastinating
      I always put off the reading. I think I will retain more if I read a few days before and retread if I don't understand something than waiting til the night before to read.
      I tend to procrastinate all my classes and come up with excuses on why I cant work on things for the classes, but I need to stop procrastination, lets hope I don't procrastinate that too.
      Come to class more prepared and begin studying for quizzes,etc sooner.
      I tend to wait till the last minute for everything.
      I have been losing easy points because I put off doing the reading assignments and then I forget and it's too late. I need to just do it right as soon as I have a gap of free time.
      I've been a procrastinator my entire life and yes I'll admit. I guess I intend to quit procrastinating until Tuesday, yet with work its always tends to happen. I will attempt to stop.
      I need to stop procrastinating and waiting till the last minute to study for quizzes and tests and I should do my reading over the weekend before its due.
      I wait till the last minute to get ready for quizzes and I really shouldn't. So i'm going to try and start studying a least a day before the quiz or test.
      This is my busiest semester ever at 5 classes. Astronomy is the only class I have 1 day a week (as well as lab, but that's all done in-class with no homework). I try to do all my other stuff and usually end up saving Astronomy stuff for last.
      A few times I've crammed all of the reading and studying to a day before class. It's really stressful to have to conquer that much information in one day and try to remember it. Even though I don't have class all day Wednesday (the day before) I still need to remember to space out my studying and reading because it's really just too hard on myself to do it all in one day.
      Stop rushing the homework and reading, and giving myself more time to complete the study questions by beginning them sooner.
      I tend to procrastinate studying until the day or night before the test or quiz, and I need to actually put more time into studying!
      I wait too long to read the book and it is too late.
      I need to not put studying off until the day before. I don't do this all the time, but often enough that I would consider it a problem I need to address! When I put things off until the last it makes it so I am rushed and stressed and the time that I do spend studying is thereby not as effective.
      Last quiz i began studying a few days in advance and noticed a substantial positive change in my quiz score.
      Sometimes I will wait last minute to start reading.
      I need to quit procrastinating and quit waiting till the last moment to do the online reading assignments.
      Stop leaving everything to the last minute, do assignments and studying days before the class they are due, so then I can review the day before class.
      I've been struggling with procrastinating lately due to a busy schedule which makes me want to relax and take breaks. But I have to keep reminding myself that I can't put things off till the last minute.
      I need to stop waiting until the last minute to do the online homework or study for quizzes.
      I intend to start doing my homework such as online reading assignments as early as time permits to fully understand the content of the course without the pressure of finishing before the assigned due date. This involves QUITTING to do my reading assignments the night before they are due.

skimming
      I tend to rush through the presentations as fast as I can in order to get my homework done quickly, and I really need to slow down and re-read.
      I've been skimming the reading just enough to do the homework and then telling myself I'll go back and read it in full after class. Problem is I only go back sometimes, and even then it's usually not until right before the quiz/test and it's too much information to inhale. I need to quit slacking!
      Read more patiently so I don't miss ez points.

skip class
      I've missed more class than I would like for various reasons and I don't consider some of my absences to be worth it
      I'm going to go to class and quit being a lazy bum and miss out on taco wednesday because i work during taco tuesday.
     I have class on Wednesdays from 11-8, and sometimes it's hard to stay motivated to stay the entire day. I get tired and hungry and just want to go home.

slacking
      It is not a good idea to just look at the presentations and skim the reading! I need to spend more time with the book!
      slacking gets you 15/40 on quizzes!
      I sometimes just skim chapters instead of reading... I'll stop that.
      I am gonna spend more time preparing for the next midterm and the quizzes.
      I intend to quit making excuses of why I have no time to study and why I cannot grasp the information, i just need to put in the time and effort and make myself do it so that I can walk away with a good grade and some great knowledge.
      i need to not be lazy and not study

stressing out
      This class is kind of difficult because of all of the new terms, diagrams, theories, and astronomers. I am the kind of person that tends to get overwhelmed and feel anxiety if I don't understand something immediately. This is was happened for the first three quizzes and I did really bad on them. I am going to quit getting so stressed out and try to take the course section by section. Also, I think if I QUIT skimming the book and START reading it, this will help a lot.
      Sometimes all the separate reading assignments between this class and the lab feel like a lot, but i manage to do them every week with relative ease so its nothing to really stress over.

TV
      I'll spend less time watching TV, and replace that with studying.

worrying
      I find that it is best not to worry about this class (or any for that matter) just prepare myself the best that i can for what's to come. At the beginning of the semester, i did not feel too well about this class because the teaching method felt odd and foreign to me - somewhat cold. I was apprehensive and wondered if the material would eventually sink in. Well, little by little, it has and now i enjoy this class because I'm more comfortable and familiar with the flow. There are still moments of overwhelm with the concepts, but i realize that's just the nature of the subject. I worry less about how well i will do in the class and consequently I am doing ok.
Start word tags:
ask questions
      Ask more questions to P-dog in class, at the end of class and even in office hours. I have endless amounts of questions and I feel P-dog has endless amounts of answers.

earlier
      I want to read the trxt earlier so I can comprehend it better. I'm going to start studying materials right before class on quiz days, that way I have everything fresh in my mind!
      I've always sort of struggled to keep on consistent reading, I tend to more read in bulk periods of time. Otherwise known as "cramming".
      Get prepared before it hits so I can maintain points!
      I intend to START studying several nights a week a little at a time to guarantee my success on exams given throughout the rest of the semester in this course.
      i have a tendency to procrastinate so i intend to start getting a head start on homework and assignments.

extra-credit
      I want to get an A in the class so I'm going to start doing any and all extra-credit available!

flashcard questions ("peer-instruction," "think-pair-share")
      I am going to start making it a habit to complete the flashcard packets before each quiz. I did this for quiz #4 and I did really well on it. Also, I started printing out the in class activities so that I can take a completed copy home for future reference.

go to class
      I have been missing too many classes due to medical reasons but I intend on starting to have good attendance again. I will also try to explain things more in group settings rather than just listening to what the other people have to say about how they got the answer.
      Show up for your lecture. When I come to class, I do not have to study nearly as much and the concepts are much more clear.
      Actually i think i only missed on class and that was because of a really bad case of poison oak. But having missed it is bothering me.

in-class activities
      I need to study more and make sure I understand the worksheets we do in class, since those are what we need to know along with flashcards questions for the test!

manage time
      Ok, this is something I realize half way through EVERY semester and you'd think I'd learn. I am doing slightly better in this area but not quite good enough to be satisfactory! I always spend time studying in my larger windows of time, but in waiting for those time blocks I allow homework and studying to stack up. If I made more use of smaller time blocks and had daily vs. weekly studying goals I am sure it would break it up more and make it all less overwhelming.
      I have a super busy school/work schedule so I need to figure out how to set aside more time for my schoolwork.

pay attention
      Paying more attention to the in class activities and making sure that I either take a copy home or take a picture so I can recall later what we did in class.
      This astronomy class is a long one and it runs right through dinner time, these two factors work against me being able to pay attention and stay focused during the class. I will start reminding myself of my goal and that paying attention will help in the long run.

reading
      I'm going to look over the presentations and blogs more often.
      I plan to read more of the text instead of just skimming.
      I'm going to start reading the chapters better. I start out pretty good and I would read them all but lately I have been skimming and I need to start reading the whole chapter again so I get all the information and not just pieces of it. I think it will help me understand the class better.
      I skim through the book stuff, or will read up something that goes with in-class assignments. Reading should probably help me, because it's the only thing I'm really cutting anything out of for this class.
      I'm not very good at reading comprehension especially when its a large amount of material. I need to start giving myself more time to read everything fully and clearly and to take notes as I go along. Reading more would help my overall better understanding of the material. I need to give myself more time to complete everything I need to do at home.
      As well as this class I'm taking four other challenging classes, and because this class is one day a week I tend to push the reading until it is too late. By not reading I'm not fully understanding the topics, so I'm going to start reading.
      (Honestly) I tend to spend most of my time studying in this class by reading the presentations. I have been doing quite well so far, but I know I need to start actually reading the book. It's hard because my other class loads are heavy as well, and its hard to find the time to sit and read *especially when I hate reading*. Though, I do intend to start reading the book in order to succeed or at least do better in class.

reviewing
      I should start reviewing everything we have learned and taking notes on it again. I think that on the midterm I got a little messed up when I had to do things we first learned because I hadn't reviewed it enough.
      I need to start going over more regularly lecture material and notes I take in the book because I get them at the time but mentally lose the concepts by the time the test rolls around.
      Review and go over my notes, textbook, and study guides beforehand so they are fresh in my mind, making sure to highlight or note the important concepts to look over later on instead of the entire passage.

study group
      I can START doing better by studying more for the quizzes to make sure I know everything. I can also study more with others so they can help if I have questions and we can work together to study and get the correct answers.

studying
      I'm going to study harder and hopefully succeed in this class and start being more efficient in this class
      I need to start studying well before the quizzes and tests in order to improve my grade.

take notes
      Taking notes because there are stuff you say in the lecture that is important to what is on the quiz or midterm and I won't be getting it down on paper to read it later when I come to that point to study. So I hope to start taking more notes and start asking questions if I don't understand something.
      I am beginning to take more thorough notes from our assigned reading sections. I find that I can clarify materials to myself by going over them outside of class in my own time and rhythm. This seems to be helping me retain and absorb the material better.
      Write down review terms and quizzes as I go a long.
      Taking notes in class will help me retain more information and stay tuned in
      I don't usually take notes in this class, however, I think it will be helpful to look over them for quiz/exam studying.

20140329

Online reading assignment question: interesting Midterm 1 physics topics

Physics 205B, spring semester 2014
Cuesta College, San Luis Obispo, CA

"20140329-interesting"
https://flic.kr/p/mzenHt
Originally uploaded by Waifer X

Wordle.net tag cloud for interesting topics covered in Midterm 1, generated by responses from Physics 205B students at Cuesta College, San Luis Obispo, CA (http://www.wordle.net/show/wrdl/7700708/Untitled).

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.

List at least five words describing interesting subjects covered in class (up through this midterm). (Graded for completion.)

Describe your most interesting subject, and briefly explain why this subject interested you. (Graded for completion.)


The following are all of the student responses, verbatim and unedited.
"I enjoyed learning about single slit and double slit interference and how they relate to things like CDs/DVDs and even how you can determine the width of a strand of hair using these principals I really like the ray diagrams because you can draw it right and get the answer."

"Something interesting is myopia, hyperopia, and how being nearsighted or farsighted needs corrective lenses that are convergent or divergent."

"I actually like the ray tracing part of this midterm. It seemed complicated at first, but the many different parts make it more interesting."

"destructive interference. I don't quite know why, but I was super interested in this topic. Light fascinates me and its so interesting how it can cancel itself."

"Definitely diffraction and total internal reflection"

"Corrective optics was the most interesting to me because I wear contacts. It was interesting to find out what kind of lens I wear and I realized that my vision is very bad because my prescription is -4.75 diopters."

"I personally found polarization very interested in the way that it works and the amount of light transferred."

"The most interesting subject covered in this midterm would have to be constructive vs. destructive interference for me. It interested me because it was a subject I was able to really grasp the best."

"i really enjoyed learning about light refraction. I think that it is interesting that you could think something is not where it actually located due to light. also polarization. i forgot to order the polarized lenses for my glasses no i see the lens glare."

"Little here has direct application to my major beyond perhaps polarization, but getting to the start of electricity has the most personal interest to me for hobbyist purposes."

"Optics. Although I could relate most everything covered to 'real life', I really had no idea how any sort of lenses worked, and, of course, I use them a lot."

"I enjoyed learning about the relationship between the wavelength, frequency, and speed of light. This interested me in part because I could understand it and how they effect each other when altered."

"The most interesting subject covered in the midterm are the lens problems. I find this subject interesting because it was easy to follow once I was able to understand the basic concept of the equation and how it functioned."

"I like energy fields because they make sense to me"

"Interference (constructive and destructive). I think it's really cool how waves can be amplified and demolished to theoretically nothing by changing distance or putting the waves in or out of source. Also, how the concept applies to slit interference and creates the minimas and maximas."

"I enjoy learning about electric fields, because it makes the most sense to me and I feel as if it has a lot of 'real world' applictions"

"Think the most interesting topic we have covered this far, for me personally anyways, would have to be how light travels through a diverging and converging lens, with the ray tracings being my main center of focus. They made no sense whatever in my mind starting out, but once I figured out how to use the ruler properly and determine where each line went, based on whether it was converging or diverging, I experienced the greatest sense of satisfaction at having discovered something completely new and foreign to me."

"I thought total internal reflection was really interesting, I think it's really cool why diamonds are so awesome."

"The most interesting subject covered in this midterms is optics. Luckily it is interesting to me because I work at an optometrist office and will be going to optometrist school. This information helps me understand corrective optics. I have also had to wear corrective lenses since grade school so this stuff is relevant to my vision accuracy."

Online reading assignment question: confusing Midterm 1 physics topics

Physics 205B, spring semester 2014
Cuesta College, San Luis Obispo, CA

"20140329-confusing"
https://flic.kr/p/mzenF4
Originally uploaded by Waifer X

Wordle.net tag cloud for confusing topics covered in Midterm 1, generated by responses from Physics 205B students at Cuesta College, San Luis Obispo, CA (http://www.wordle.net/show/wrdl/7700707/Untitled).

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.

List at least five words describing confusing subjects covered in class (up through this midterm). (Graded for completion.)

Describe your most confusing subject, and briefly explain why this subject interested you. (Graded for completion.)


The following are all of the student responses, verbatim and unedited.
"I really just can't get the hang of two lens systems. It just hasn't clicked yet, but hopefully by sometime tonight it will"

"I really don't like the electric fields. I have a lot of confusion about the different variables and what they are."

"The difference between refraction and reflection."

"I had most trouble with the thin lens equations and diopters. I wasn't exactly sure how to relate them and use them when given a certain situation."

"Maybe I was daydreaming in class that day, but I really have a hard time with frequencies"

"Fields!! Ahhhhh!!!"

"The maxima/minima were the most confusing because I was sick so I missed that class. I also feel like for every problem we use 1 as the maxima/minima so I don't see the point. But that's probably because I was not in class."

"I struggled with charges of electrons"

"I got really confused with single-slit and double-slit material. Although I can see when they are being used in life situations, it wasn't something I was more easily able to comprehend and grasp. I have to say though, the lab was very interesting and helpful."

"i am very confused still on how to figure out whether a charge is going to be positive or negative."

"I suppose that some of the things involving thin-lens equations and the signs of different variables is a bit annoying. I'm not fond of just memorizing things."

"I was confused, up to the last quiz, about if electrons actually transfer from object to object."

"Like in the ball and rod example. Maybe I missed or can't remember it, and although I understood how to do the problems, I never really "got" wave diffraction. Never really understood the bigger picture or its application, besides measuring distances between tracks on a DVD."

"I found the lenses to be confusing because I have difficulty understanding how changing certain quantities will change the image."

"The most confusing subject was the single and double slit portion of the chapters. I was not able to fully understand how the double slit and single slit equations worked or why they worked the way they did. it just did not make sense to me"

"i don't get how constructive and destructive lenses work"

"Electric fields and how they relate to the electric potential and electric potential energy. These just seem to overlap and sound so similar that I get confused what is happening and what is causing each phenomenon."

"The most confusing subject covered in this midterm for myself had to deal with converging and diverging lenses and the images they produced as virtual vs real and upright or inverted. This was personally confusing because I did not fully understand what was going on and how an image can be upright or inverted and if it was real or virtual."

"The different conditions of the eye. I can never keep them straight."

"Think the most confused I have been thus far was during our continued discussion of resistors and circuits. Coming in at a close second would have to be differentiating between real and virtual images when viewed through a lens. I don't know, I guess I just can't seperate this from that in terms of characteristics that determine whether the image is real or virtual."

"The single slit/double slit material is the most confusing for me, I think because I missed the class that covered it. :("

"Electric fields and circuits are confusing to me. I have a harder time relating them to things that are relevant or interesting to me in my everyday life."

Online reading assignment question: helpful/unhelpful Midterm 1 physics study tips

Physics 205B, spring semester 2014
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.

Describe something notable that either helped or did not help with studying for this midterm. Selected comments may be discussed in class. (Graded for completion.)

The following are all of the student responses to this question, verbatim and unedited.
"Working out problems that help demonstrate the relationship between variables/parameters"

"Creating a study guide as you go through what will be on the test. Like a cheat sheet."

"Something that helps is going over notes and focusing on last springs midterm as well as the questions mentioned on monday in the calender."

"Remembering the ray tracings help a lot!"

"the previous years mid term was super helpful"

"Repetition, repetition, repetition.."

"Doing the homework in class on the whiteboards was definitely the biggest help. It brought together everything I learned in class and helped me know exactly what I needed more practice with."

"The worked out problems from past midterms"

"Going over class notes, especially notes taken on example problems, were really helpful. Also photos that were posted of notes you wrote on the board were also great review."

"knowing what problems are on the midterm is really helpful, but i would like to see more description on why the answers are p because sometimes the student reached it algebraically and i need a theoretical answer."

"The tinker toy teaching aid was a good tangible model of unpolarized waves."

"Well, mainly, studying what you have outlined for us and working out the problems in your blog."

"I found it helpful to do all the example problems from previous years, as they are comparable to the difficulty of problems that will likely be on the midterm."

"it does not help to study last minute but it does help to go through all the review problems and try to do them more than once until you do not need to look at any notes"

"Using the online blog helps the most by far."

"Get a big study group and work out problems on a white board and talk to each other about any confusion about concepts."

"its helpful to know what topics are on the exam"

"Past similar questions are posted from the midterm these seem like a great way to get an idea of how well you have to know the concepts."

"Drinking caffine is said to improve exam scores because it allows the mind to focus longer than the average 20 minutes as well as retention of material has been shown to improve with those that have caffine."

"Doing the practice problems helps me the most."

"Even you don't really feel like it, sometimes you just have to fight your better senses and just dive right into the practice midterm and past lectures in order to improve the things that need improvement the most. Not going to lie, I get frustrated when I cannot immediately figure out an equation or concept, but it does not do any good just to throw it to the side and tell yourself you will deal with that crap later. Do it now! With a little determination, you are totally capable of figuring it out!"

"Not having the key for the flashcard questions doesn't help. But the explanations for certain quiz questions on the blog does help."

"Doing practice problems helps tremendously!!"

Physics midterm question: implausible Instagram filter

Physics 205B Midterm 1, spring semester 2014
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 23.65


Two photos[*][**] of the same sunset are shown above, where the second image apparently has a fishbowl effect added to it. Assuming that this fishbowl is a spherical glass bowl filled with water, discuss why this second image cannot be a plausible realistic effect. Explain your reasoning using the properties of lenses, thin lens equations and/or ray tracings.

[*] weheartit.com/entry/91939793/via/_Lientje.
[**] instagram.com/p/kuXP8jq0a9/.

Solution and grading rubric:
  • p:
    Correct. Understands that (a) a spherical fishbowl filled with water would behave as a converging lens, and uses a ray diagram, thin lens equation(s), and/or properties of lenses in general to discuss contradictions due to either (i) sun and horizon well outside of the focal point of converging lens should produce a diminished, inverted image (which is instead upright and appears to be the same size), or (ii) upright image must be virtual, which can only be caused by object well inside of the focal length of a converging lens (not plausible for the sun/horizon), or an object near a diverging lens (which would not be a spherical water-filled fishbowl).
  • r:
    As (p), but argument indirectly, weakly, or only by definition supports the statement to be proven, or has minor inconsistencies or loopholes.
  • t:
    Nearly correct, but argument has conceptual errors, or is incomplete.
  • v:
    Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
  • x:
    Implementation/application of ideas, but credit given for effort rather than merit.
  • y:
    Irrelevant discussion/effectively blank.
  • z:
    Blank.
Grading distribution:
Sections 30882, 30883
Exam code: midterm01b0w7
p: 15 students
r: 8 students
t: 13 students
v: 3 students
x: 2 students
y: 0 students
z: 0 students

A sample "p" response (from student 1216):

Physics midterm question: moving interfering transmitters back from receiver

Physics 205B Midterm 1, spring semester 2014
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 25.1

A radio antenna receives a destructive interference signal from two transmitters that broadcast in phase at the same wavelength. Discuss why the radio antenna will still receive a destructive interference signal if both of the two transmitters are each moved one-half of a wavelength farther away from their current distances from the radio antenna. Explain your reasoning by using the properties of waves and interference.

Solution and grading rubric:
  • p:
    Correct. Recognizes that (a) the two waves from in phase sources interfere destructively, so the path length difference ∆l = (m + 1/2)∙λ, and (b) demonstrates by either drawings or explicit math how extending both paths by half a wavelength will not affect the path length difference, thus the interference will still be destructive as stated.
  • r:
    As (p), but argument indirectly, weakly, or only by definition supports the statement to be proven, or has minor inconsistencies or loopholes. Typically recognizes that ∆l will not be affected by moving both transmitters by half a wavelength, but does not explicitly demonstrate how this is so.
  • t:
    Nearly correct, but argument has conceptual errors, or is incomplete.
  • v:
    Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
  • x:
    Implementation/application of ideas, but credit given for effort rather than merit.
  • y:
    Irrelevant discussion/effectively blank.
  • z:
    Blank.
Grading distribution:
Sections 30882, 30883
Exam code: midterm01b0w7
p: 14 students
r: 14 students
t: 11 students
v: 1 student
x: 1 student
y: 0 students
z: 0 students

A sample "p" response (from student 5297):

Another sample "p" response (from student 3420):

Physics midterm problem: Foldscope magnification claim

Physics 205B Midterm 1, spring semester 2014
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problems 23.57, 24.29

The Foldscope is a low-cost "origami-based paper microscope"[*] designed by Stanford University researchers to be used for science, medicine, and education in developing countries.[**] It has a single converging lens that can either project an enlarged real image on a screen, or be used as a simple magnifier. When used as a projector, the object distance and image distances are 0.24 mm and 100.00 mm, respectively. When used as a simple magnifier, determine whether or not it is plausible that the angular magnification obtained with this Foldscope could be as high as the stated value of 1,140×. (Use the nominal value of 250 mm for the near point.) Show your work and explain your reasoning.

[*] "MAG (angular magnification) = 1,140×," arxiv.org/pdf/1403.1211v1.pdf.
[**] ted.com/talks/manu_prakash_a_50_cent_microscope_that_folds_like_origami.

Solution and grading rubric:
  • p:
    Correct. Determines (a) the focal length of the lens using the thin lens equation, and (b) the resulting angular magnification when used as a simple magnifier, which is slightly less (1,044×) than the stated value (1,140×). May either argue that claim is plausible or implausible with these values.
  • r:
    Nearly correct, but includes minor math errors.
  • t:
    Nearly correct, but approach has conceptual errors, and/or major/compounded math errors. At least has focal length of lens, but compares linear magnification of projected real image instead of angular magnification of virtual image when used as a simple magnifier.
  • v:
    Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner.
  • x:
    Implementation of ideas, but credit given for effort rather than merit. Use of other optics equations, etc.
  • y:
    Irrelevant discussion/effectively blank.
  • z:
    Blank.
Grading distribution:
Sections 30882, 30883
Exam code: midterm01b0w7
p: 29 students
r: 2 students
t: 4 students
v: 6 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 7810):

Another sample "p" response (from student 2419):

Physics midterm problem: known and unknown source charges exerting forces on test charge

Physics 205B Midterm 1, spring semester 2014
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 16.15

Two point charges are held at fixed locations. An unknown charge is at 
x = –40 cm, and a –6.0 µC charge is at x = +15 cm. A +4.0 µC test charge placed at the origin experiences a force of 2.4 N, directed to the left. Determine the sign (±) and amount of the unknown charge (in either coulombs or µC) that is located at x = –40 cm. Explain your reasoning using properties of electric forces, fields, and vector superposition.

Solution and grading rubric:
  • p:
    Correct. Identifies (a) two source charges (Q1 = unknown charge at x = –40 cm; and Q2 = –6.0 µC charge at x = +15 cm) that exert forces on the test charge q = +4.0 µC at the origin. Then determines that since the net force on the q = +4.0 µC test charge is to the left: (b) the Q2 = –6.0 µC source charge attracts (pulls to the right) the q = +4.0 µC test charge, such that the unknown source charge Q1 must be negative in order to attract (pull to the left) the q = +4.0 µC test charge; and (c) finds the magnitude of the unknown source charge Q1 by setting up the superposition of the two force vectors on the q = +4.0 µC test charge, which is the difference of the magnitudes (due to the forces being in opposite directions), setting this equal to the total force on the test charge F = 2.4 N, and then solves for the unknown source charge Q1, which is –53 µC. May have slight but very minor conversion, arithmetic, and/or misplaced numerical values that do not substantively affect the conceptual understanding of setting up the proper vector addition.
  • r:
    Nearly correct, but misidentifies source charges and test charge. As (p), but identifies the unknown charge at x = –40 cm as the test charge q, having a force of 2.4 N exerted on it (either to the left or right); and the two source charges exerting forces on the unknown test charge q are Q1 = +4.0 µC at the origin, and Q2 = –6.0 µC at x = +15 cm. (In this case the numerical result for the amount of unknown test charge q = |52 µC| is coincidentally very similar to the different situation as originally described in the statement of the problem, and as executed as described in (p).)
  • t:
    Nearly correct, but approach has conceptual errors, and/or major/compounded math errors. At least has some attempt at identifying and executing the vector addition of two sources charges exerting forces acting on (or creating electric fields acting at the location of) a test charge.
  • v:
    Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner. Typically only evaluates one of the force vectors on the charge, or one of the electric field vectors at that location to determine the unknown charge.
  • x:
    Implementation of ideas, but credit given for effort rather than merit. Some constructive attempt at finding the force or electric field to determine the unknown charge.
  • y:
    Irrelevant discussion/effectively blank.
  • z:
    Blank.
Grading distribution:
Sections 30882, 30883
Exam code: midterm01b0w7
p: 9 students
r: 13 students
t: 9 students
v: 10 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 1391), using a direct force approach:

Another sample "p" response (from student 7979), instead using a two-step electric field approach:

A sample "r" response (from student 3420), using a direct force approach with the unknown charge at x = -40 cm being the test instead of a source charge:

Another sample "r" response (from student 0001), instead using a two-step electric field approach with the unknown charge at x = -40 cm being the test instead of a source charge:

20140328

Astronomy current events question: Kepler data "verification by multiplicity" planet discoveries

Astronomy 210L, spring semester 2014
Cuesta College, San Luis Obispo, CA

Students are assigned to read online articles on current astronomy events, and take a short current events quiz during the first 10 minutes of lab. (This motivates students to show up promptly to lab, as the time cut-off for the quiz is strictly enforced!)
Elizabeth Howell, "Mega Discovery! 715 Alien Planets Confirmed Using A New Trick On Old Kepler Data," February 26, 2014
http://www.universetoday.com/109764/mega-discovery-715-alien-planets-confirmed-using-a-new-trick-on-old-kepler-data/
NASA researchers confirmed the existence of 715 new extrasolar planets by assuming regular transits across a star are more likely to be caused by planets instead of:
(A) random noise.
(B) solar flares.
(C) sunspots.
(D) companion stars.
(E) moons.

Correct answer: (D)

Student responses
Sections 30678, 30679, 30680
(A) : 0 students
(B) : 2 students
(C) : 1 student
(D) : 31 students
(E) : 9 students

Astronomy current events question: central supermassive black hole and G2 dust/gas cloud

Astronomy 210L, spring semester 2014
Cuesta College, San Luis Obispo, CA

Students are assigned to read online articles on current astronomy events, and take a short current events quiz during the first 10 minutes of lab. (This motivates students to show up promptly to lab, as the time cut-off for the quiz is strictly enforced!)
Adam Mann, "Scientists May Get Best View Yet of a Black Hole in Action," March 14, 2014
http://www.wired.com/wiredscience/2014/03/black-hole-snack-time/
Telescopes all over the world will be observing the Milky Way's supermassive black hole as it interacts with:
(A) slowing down time.
(B) x-ray pulsar beams.
(C) a nearby gas/dust cloud.
(D) surrounding dark matter.
(E) a possible wormhole.

Correct answer: (C)

Student responses
Sections 30678, 30679, 30680
(A) : 0 students
(B) : 2 students
(C) : 26 students
(D) : 3 students
(E) : 2 students

Astronomy current events question: ringwoodite and water beneath Earth's crust

Astronomy 210L, spring semester 2014
Cuesta College, San Luis Obispo, CA

Students are assigned to read online articles on current astronomy events, and take a short current events quiz during the first 10 minutes of lab. (This motivates students to show up promptly to lab, as the time cut-off for the quiz is strictly enforced!)
Bryan Alary, "Rare Mineral Points to Vast 'Oceans' Beneath the Earth," March 12, 2014
http://news.ualberta.ca/newsarticles/2014/march/rare-mineral-points-to-vast-oceans-beneath-the-earth
An international team of scientists discovered a mineral in a diamond which indicates:
(A) it was not created by volcanic heat and pressure.
(B) Earth's oceans came from comet impacts.
(C) carbon-based life began in volcanic ocean vents.
(D) diamonds are extremely common.
(E) large amounts of water lie under Earth's crust.

Correct answer: (E)

Student responses
Sections 30678, 30679, 30680
(A) : 7 students
(B) : 2 students
(C) : 3 students
(D) : 0 students
(E) : 30 students

20140326

Online reading assignment: stellar parameters (SLO campus)

Astronomy 210, spring semester 2014
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 parallax, distance, apparent magnitude, absolute magnitude, Wien's law and the Stefan-Boltzmann law.

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.
"Stars are hot, yo!"

"Its interesting that it seems like a lot of stuff in astronomy is backwards. For example, someone would want to originally consider a red thing to be hotter but no its actually blue thats hottest. And that blackbody radiation would have to do with blackness but no it actually has to do with glowing objects instead. It all seems like it's meant to trick us."

"As an art major, I found it interesting that stars follow a sort of 'reverse order' for their color to temperature relation; in art cooler colors are blue, green, purple, and warmer colors are red, orange, and yellow. Stars, however, the hottest appear white or blue in color, while the coolest appear reddish."
I'm just shocked I didn't know the order of the brightness and temperature of stars."

"I was surprised that blue stars were the hottest, assumed they were going to be much cooler than the red and orange stars."

"I think its interesting that the temperature of a star affects the color, I always figured the color depended upon the gases that made up the star."

"I found luminosity and Wien's law to be pretty interesting with the how a star's distance can be measured in its color. I don't know why, it's just always rang as pretty cool to me that we humans can judge the temperatures stars around Earth, all based in colors."
"For some reason I always thought that brown dwarf stars were really hot. But it's actually the complete opposite and I found that very interesting."

"I am not finding any of it interesting."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"How to determine the distance of stars--basically that whole thing."

"For me I found it interesting how you find the luminosity of a star based on the size and temperature, or maybe it is the size you are finding out based on the luminosity and temperature , I'm not really sure what is going exactly so some explanation here would be helpful."

"I didn't find anything particularly confusing."

"Please please pleassse go over the H-R diagram. I know it would be helpful if I could read it better."

"I don't really understand the definition of absolute visual magnitude. What I'm grasping is that it's the brightness if the star was moved to 10 parsecs (making it obvious which stars are brighter because they're all equally distant)."

"I did not find any of the information interesting because it is all confusing to me. "

"Measurements of stars? Makes me think of math and I am not good at it."

Explain how apparent magnitude and the absolute magnitude are defined differently.
"Absolute magnitude is the actual real brightness of the star. Apparent magnitude is only how bright it appears as seen from Earth."

"Apparent magnitude is how bright the star appears at its actual distance, while absolute magnitude is the brightness the star would have if it was moved to 10 pcs away."

"Apparent: what it looks like from Earth. Absolute: what it actually is."

Suppose the sun was moved to a distance of 10 parsecs away. As a result, its __________ magnitude would become dimmer.
absolute.  ******** [8]
apparent.  ************************** [26]
(Both of the above choices.)  ** [2]
(Neither of the above choices.)  * [1]
(Unsure/guessing/lost/help!)  [0]

Rank the temperatures of these stars (1 = hottest, 4 = coolest; there are no ties).
(Only correct responses shown.)
Hottest: blue supergiant [97%]
Second hottest: white dwarf [78%]
Third hottest: yellow supergiant [81%]
Coolest: red dwarf [97%]

Two stars (equally far away) have the same temperature, but one star is dimmer, and the other star is brighter. The __________ star will be larger in size.
dimmer.  ** [2]
brighter.  ******************************* [31]
(These stars would be the same size.)  * [1]
(Unsure/guessing/lost/help!)  *** [3]

Two stars (equally far away) have the same brightness, but one star is cooler, and the other star is hotter. The __________ star will be larger in size.
cooler.  *************** [15]
hotter.  *************** [15]
(These stars would be the same size.)  *** [3]
(Unsure/guessing/lost/help!)  **** [4]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I really enjoy the diagrams you draw on the board. I find them very helpful and resourceful. Not to mention I like copying them and making them cute in my notebook--it's a girl thing."

"Why did I not know about all the help on your blog? I feel like an idiot lol." (Duh-doy.)

"How do you feel about how well the 'flipped class' is working?" (As much as I like the format, I do have to be a scientist about it, so I'm gathering data to find out how much you are learning (versus my traditional classes from previous semesters), and will be evaluating this hypothesis eventually.)

"Will we be using the telescopes in class anymore to look at the stars and planets?" (I will try to schedule another observatory visit soon, either before class (to look at sunspots during the day) and/or after class at night (to see Jupiter, the Orion Nebula, the Pleiades, and other cool stuff.)

"How many more extra-credit opportunities will be available?" (As many as you need. At least two more this semester.)

"I tried miso soup and all I could think about was convection currents."(And how tasty it was, right? RIGHT?)

"I heard that the sun is in a binary system with another star, is this true?" (Previously, maybe. But NASA Wide-field Infrared Survey Explorer (WISE) space telescope results announced earlier this month totally debunked this.)

"Were you happy with the midterm scores?" (Meh. I could be happier. You could all make me happier on the next midterm.)

20140325

Online reading assignment: stellar parameters (NC campus)

Astronomy 210, spring semester 2014
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 parallax, distance, apparent magnitude, absolute magnitude, Wien's law and the Stefan-Boltzmann law.

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 found the idea of surveying the stars interesting because I had no idea so much of the universe has already been mapped out and it's all happening in my lifetime."

"I liked reading about the distances between the stars. Measuring between such great distances is fascinating."

"Using the color of stars to determine their temperature."

"I thought it was interesting finding out that you can tell how hot a star is relative to another by color--I would have guessed it would be more complicated than that."

"The H-R diagram is very interesting to me because this is a handy visual tool to understand the luminosities and temperatures of stars and how they relate to other stars. Their spectral types are noted and whether they are in main sequence stars, supergiants, giants, red dwarfs or white dwarfs. Cool stuff."

"I found it interesting that red is cooler then blue! I thought that red was always considered a hot color and blue was a cool color."

"A simple math equation can be used to tell one of three quantities (temperature, luminosity, and brightness) of stars. Math seemed to be my strongest subject."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"I found measuring the distance of stars confusing. There are a few methods but they'll all math/formula related which aren't my strong suit."

"I need clarification on absolute and apparent magnitude. I have some idea, but I'm not 100% sure."

"The process of determining the distance of a star was confusing. I think it was confusing because the parallax idea throws me off a bit."

"I still just don't really understand the whole luminosity thing and how the size makes the star dimmer or brighter."

Explain how apparent magnitude and the absolute magnitude are defined differently.
"Absolute is the intrinsic brightness of a star. Apparent is only how bright stars appear from Earth."

"The absolute magnitude is the apparent magnitude that star would have if it were 10 parsecs away (standard distance)."

"Absolute magnitude versus apparent magnitude is hard for me to explain."

Suppose the sun was moved to a distance of 10 parsecs away. As a result, its __________ magnitude would become dimmer.
absolute.  ********** [10]
apparent.  *********** [11]
(Both of the above choices.)  **** [4]
(Neither of the above choices.)  [0]
(Unsure/guessing/lost/help!)  [0]

Rank the temperatures of these stars (1 = hottest, 4 = coolest; there are no ties).
(Only correct responses shown.)
Hottest: blue supergiant [88%]
Second hottest: white dwarf [52%]
Third hottest: yellow supergiant [60%]
Coolest: red dwarf [84%]

Two stars (equally far away) have the same temperature, but one star is dimmer, and the other star is brighter. The __________ star will be larger in size.
dimmer.  ****** [6]
brighter.  ****************** [18]
(These stars would be the same size.)  [0]
(Unsure/guessing/lost/help!)  * [1]

Two stars (equally far away) have the same brightness, but one star is cooler, and the other star is hotter. The __________ star will be larger in size.
cooler.  ************ [12]
hotter.  ************ [12]
(These stars would be the same size.)  * [1]
(Unsure/guessing/lost/help!)  [0]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I like how in the book they compare the H-R diagram to a diagram about horsepower vs. weight for cars. It gave me a better understanding of how the H-R diagram works."

"This star talk is really moving us into an interesting chapter!"

"This is great learning more about the stars and their temperatures. Can't wait to learn more."

20140324

Education research: formative SASS student learning outcomes assessment (Cuesta College, spring semester 2014, first midterm)

Student achievement of course learning outcomes are assessed by administering an Student Assessment of Skills Survey (SASS), a five-point Likert scale questionnaire (Patrick M. Len, in development) to Physics 205B students at Cuesta College, San Luis Obispo, CA. This is the second semester of a two-semester introductory physics course (college physics, algebra-based, mandatory adjunct laboratory).

Different sections of the SASS are administered online just before each of two midterms, and the final exam.

The SASS results from the first midterm of the semester are compiled below. Values for the mean and standard deviations are given next to the modal response category for each question. Listed are the percentages of students who have self-assessed themselves as having successfully achieving a learning outcome (responding "average," "above average," or "excellent") as opposed to not achieving success with a learning outcome (responding "very poor" or "below average").

Cuesta College
Student Assessment of Skills Survey (SASS)
Physics 205B spring semester 2014
Sections 30882, 30883
N = 39

The questions below are designed to characterize your achievement of each of the learning outcomes by filling in a bubble on the rating scale provided to the right of each statement.

Mark the level of achievement that best describes your learning at this time.

1. Understand the relationship between wave properties and parameters (frequency, speed, velocity, wavelength, refraction indices, etc.) of light.
(Achieved: 87%, unachieved: 13%)
Very poor.  * [1]
Below average.  **** [4]
Average.  ***************** [17]
Above average.  ************* [13]
Excellent.  **** [4]

2. Analyze and describe the behavior of antennae, ideal polarizers and scattering on the polarization of light.
(Achieved: 74%, unachieved: 26%)
Very poor.  *** [3]
Below average.  ******* [7]
Average.  *************** [15]
Above average.  *********** [11]
Excellent.  *** [3]

3. Describe and analyze reflection, refraction, and total internal reflection using the law of reflection and Snell's law.
(Achieved: 85%, unachieved: 15%)
Very poor.  ** [2]
Below average.  **** [4]
Average.  ****************** [18]
Above average.  ************* [13]
Excellent.  ** [2]

4. Analyze and describe characteristics (real/virtual, upright/inverted, magnified/diminished) of images produced by lenses using the thin lens equation, magnification equation, and ray tracings.
(Achieved: 62%, unachieved: 38%)
Very poor.  * [1]
Below average.  ************** [14]
Average.  ************* [13]
Above average.  ********** [10]
Excellent.  * [1]

5. Analyze and describe how the eye works (accommodation), and how vision defects can be corrected by contacts/glasses.
(Achieved: 69%, unachieved: 31%)
Very poor.  *** [3]
Below average.  ********* [9]
Average.  *********** [11]
Above average.  ************** [14]
Excellent.  ** [2]

6. Analyze and describe optical systems such as simple magnifiers, compound microscopes, and telescopes.
(Achieved: 64%, unachieved: 36%)
Very poor.  ** [2]
Below average.  ************ [12]
Average.  *************** [15]
Above average.  ********** [10]
Excellent.  [0]

7. Analyze and describe the constructive/destructive interference of two coherent waves from a phase difference due to source timing, phase reflections, and/or path differences.
(Achieved: 79%, unachieved: 21%)
Very poor.  **** [4]
Below average.  **** [4]
Average.  **************** [16]
Above average.  ************ [12]
Excellent.  *** [3]

8. Analyze and describe interference maxima and minima produced by double-slits and gratings.
(Achieved: 87%, unachieved: 13%)
Very poor.  **** [4]
Below average.  * [1]
Average.  ****************** [18]
Above average.  ************ [12]
Excellent.  **** [4]

9. Analyze and describe diffraction (only up to the first minima angle) produced by a single-slit.
(Achieved: 74%, unachieved: 26%)
Very poor.  **** [4]
Below average.  ****** [6]
Average.  *************** [15]
Above average.  *********** [11]
Excellent.  *** [3]

10. Understand how electrons behave in and can be transferred from conductors/insulators.
(Achieved: 82%, unachieved: 18%)
Very poor.  ** [2]
Below average.  ***** [5]
Average.  **************** [16]
Above average.  *************** [15]
Excellent.  * [1]

11. Analyze and describe the electric force on a charge, due to several point charges that lie along the same line using Coulomb's law, and the principle of superposition (vector addition).
(Achieved: 72%, unachieved: 28%)
Very poor.  **** [4]
Below average.  ******* [7]
Average.  **************** [16]
Above average.  *********** [11]
Excellent.  * [1]

12. Understand the relationship between the electric force on a point charge, and the electric field present at the location of that point charge.
(Achieved: 72%, unachieved: 28%)
Very poor.  *** [3]
Below average.  ******** [8]
Average.  ****************** [18]
Above average.  ********* [9]
Excellent.  * [1]

13. Analyze and describe the electric field at a specific location, due to several point charges that lie along the same line using the definition of an electric field for a single point charge, and the principle of superposition (vector addition).
(Achieved: 64%, unachieved: 36%)
Very poor.  **** [4]
Below average.  ********** [10]
Average.  ***************** [17]
Above average.  ******* [7]
Excellent.  * [1]

Of the 13 student learning outcomes in this section of the SASS, three were self-reported as being achieved by at least 85% of students, listed below in order of decreasing success:
1. Understand the relationship between wave properties and parameters (frequency, speed, velocity, wavelength, refraction indices, etc.) of light. (87%)
8. Analyze and describe interference maxima and minima produced by double-slits and gratings. (87%)
3. Describe and analyze reflection, refraction, and total internal reflection using the law of reflection and Snell's law. (85%)
10. Understand how electrons behave in and can be transferred from conductors/insulators. (82%)
7. Analyze and describe the constructive/destructive interference of two coherent waves from a phase difference due to source timing, phase reflections, and/or path differences. (79%)
9. Analyze and describe diffraction (only up to the first minima angle) produced by a single-slit. (74%)
2. Analyze and describe the behavior of antennae, ideal polarizers and scattering on the polarization of light. (74%)
11. Analyze and describe the electric force on a charge, due to several point charges that lie along the same line using Coulomb's law, and the principle of superposition (vector addition). (72%)
12. Understand the relationship between the electric force on a point charge, and the electric field present at the location of that point charge. (72%)
5. Analyze and describe how the eye works (accommodation), and how vision defects can be corrected by contacts/glasses. (69%)
6. Analyze and describe optical systems such as simple magnifiers, compound microscopes, and telescopes. (64%)
13. Analyze and describe the electric field at a specific location, due to several point charges that lie along the same line using the definition of an electric field for a single point charge, and the principle of superposition (vector addition). (64%)
4. Analyze and describe characteristics (real/virtual, upright/inverted, magnified/diminished) of images produced by lenses using the thin lens equation, magnification equation, and ray tracings. (62%)

Since this section of the SASS is administered before the first midterm, it should be considered a formative rather than summative form of self-assessment.

20140321

Presentation: circuit analysis

People in a line, holding hands: check. On top of insulating materials: check. With a person at one end of the line touching an electric fence: check. Now with the person at the other side of the line, barefoot, in touch with the ground: priceless. (Video link: "Electric fence experiment ends as expected.")

In this presentation we introduce the quantitative methods of analyzing circuits.

First, calculating equivalent resistances for different configurations of resistors.

The two basic configurations are where resistors are in series, literally "chained" together end-to-end such that current must pass through each resistor in sequence; or in parallel, where current can divide up such that portions of it can pass through several resistors simultaneously.

For most configurations of resistors, an equivalent resistance can be calculated, which represents the value of the single resistor that could replace them without affecting the rest of the circuit.

The equivalent resistance of resistors in series is their arithmetic sum, such that adding another resistor in series would increase the equivalent resistance.

For example, a 0.5 Ω light bulb and a 2.0 Ω resistor connected in series would have an equivalent resistance of 0.5 Ω + 2.0 Ω = 2.5 Ω.

In contrast, for resistors in parallel the equivalent resistance is calculated as the reciprocal of the sum of the reciprocals, such that adding another resistor in parallel would actually decrease the value of the equivalent resistance.

So if a 0.5 Ω light bulb and 2.0 Ω resistor were instead connected in parallel with each other, the equivalent resistance would be:

Req = (1/(0.5 Ω) + 1/(2.0 Ω))-1 = (2.0 Ω-1 + 0.50 Ω-1)-1 = (2.5 Ω-1)-1 = 0.40 Ω.

We'll discuss a model of why equivalent resistances work so differently for series and parallel circuits later during lecture, especially after we learn how to apply Kirchhoff's rules in the last part of this presentation.

Second, sign conventions for electric potential drops and rises in circuits.

As with this kayaker flowing downstream, or this salmon jumping upstream, positive and negative signs will denote whether we are heading "down-" or "upstream" in an electrical circuit--losing or gaining electric potential (or voltage).

Recall from Ohm's law (introduced in a previous presentation) that the electric potential (or voltage) difference ∆V between either end of a resistor can be related to the current I flowing through it, and the resistance R of the resistor.

Given that the current is flowing from left-to-right through this resistor, if we follow the current "downstream" from left-to-right, then the potential difference ∆V will drop by I·R, as the electric potential decreases in that direction. However, if we go from right-to-left, or "upstream" against the flow of current, then the potential difference ∆V will rise by I·R, as the electric potential increases in that direction.

For an emf source (such as an ideal battery) with a potential difference of ε, we do not pay attention to the direction of current flowing through the battery, but instead watch how we move through the battery with respect to the positive (+) and negative (-) terminals, which respectively represent the higher and lower electrical potential ends of the battery.

If we go through the battery from the negative (-) to the positive (+) terminals, then the potential difference ∆V will be rise by ε, as the electric potential increases in that direction. However, if we go through the battery from the positive (+) to the negative (-) terminals, then the potential difference ∆V will drop by ε, as the electric potential decreases in that direction.

These sign conventions may seem obscure, but we will need to strictly obey them as we apply Kirchhoff's rules to electric circuits.

Third, Kirchhoff's rules (finally).

Kirchhoff's junction rule is a statement of current conservation (that is, conservation of charge flow per time). The sum of all currents flowing into a junction must equal the sum of all currents flowing out of that same junction.

So basically, "what goes in must come out" (or if there are no junctions, "what comes through must go through"). This may seem like a simple concept, but it will be useful to enforce mathematically as we analyze electrical circuits, as in this tangled mess of wires.

Let's illustrate the junction rule with a series circuit (with an ideal 9.0 V battery, 0.5 Ω light bulb, and 2.0 Ω resistor). Since there are no junctions for current to go elsewhere in this circuit, this means that the resulting current of 3.6 A must not only pass through the battery, but 3.6 A of current must also go through the wire segment on the right, through the light bulb and resistor, and through the wire segment on the left to get back to the battery. (Make sure you know how to derive the value of the current in this example from the equivalent resistance of this circuit and Ohm's law, as discussed in a previous presentation.)

Now let's illustrate the junction rule with a parallel circuit (with an ideal 9.0 V battery, 0.5 Ω light bulb, and 2.0 Ω resistor). Note that there are two junctions. There is 22.5 A of current passing though the battery, and then through the wire segment on the right, and then this current splits up at the first junction, such that 18 A of current goes through the light bulb, and 4.5 A of current goes through the the battery. From the junction rule, the current going into this junction (22.5 A) must equal the currents leaving the junction (18 A + 4.5 A). The currents flowing through the light bulb (18 A) and the resistor (4.5 A) then merge at the second junction, and equal the current leaving the second junction (22.5 A), which is equal to the current going though the wire segment on the left to get back to the battery. (Again, make sure you know how to derive the current values in this example from the equivalent resistance of this circuit and Ohm's law.)

Kirchhoff's loop rule is a statement of the conservation of electric potential (that is, electric potential energy per charge). If we follow a complete loop in an electrical circuit, such that we wind up back at our starting point, all of the electric potential rises added together must equal all of the electric potential drops added together.

This is merely a consequence of having the same location as the initial and our final points as we travel around a complete loop in an electrical circuit--the voltage rises equals the voltage drops, for a "net zero" change in voltage when we arrive back at the starting point. Here Mrs. P-dog and her nephew and nieces run around a complete circuit (a playground set), running up the steps (gaining electric potential, as in traveling through an ideal battery from the (-) to the (+) terminals), and then sliding down the slide (losing electric potential, as in traveling "downstream" through a resistor), only to wind up again at their starting point, and subsequently making many, many round trips. For a complete loop, the gains equal the losses. Endless hours of entertainment. (Video link: " 20091008030.")

Let's illustrate the loop rule with the series circuit from before. Topologically, there is only one loop in this circuit. Going clockwise around this loop, in the direction of current, the rise in voltage (going from the (-) to the (+) terminal of the battery) must be equal the drops in voltage (due to current flowing through the light bulb and the battery). Numerically the 9.0 V rise in voltage from the battery must equal the 1.8 V drop in voltage due to the light bulb together with the 7.2 V drop in voltage due to the resistor. When going around this complete loop of circuit (and for any loop), all of the voltage increases must be used up by the voltage decreases.

This means that because the light bulb and the battery are wired in series to the ideal battery, they will together "share" the 9.0 V from the battery. (However, all of the current from the battery passes through the light bulb and then passes through the battery.)

Now let's illustrate the loop rule with the parallel circuit from before. Topologically, there are three possible loops (can you see all three?) but we'll only consider the two "interesting" loops to travel counterclockwise around, in the direction of current.

For the complete loop that includes the battery and the light bulb, going clockwise around this loop, in the direction of current, the 9.0 V rise in voltage (going from the (-) to the (+) terminal of the battery) must be equal to a 9.0 V drop in voltage (due to current flowing through the light bulb).

Then for the complete loop that includes the battery and the resistor, going clockwise around this loop, in the direction of current, the 9.0 V rise in voltage (going from the (-) to the (+) terminal of the battery) must be equal to a 9.0 V drop in voltage (due to current flowing through the resistor).

This means that because the light bulb and the resistor are wired in parallel to the ideal battery, they will each use the full 9.0 V from the battery. (However, current from the battery splits up and is "shared" between the light bulb and the battery.)

For the people holding hands in contact with the electric fence at the start of this presentation, there is a voltage source that maintains the fence having a higher electric potential than the ground. With a complete circuit of people holding hands to complete the circuit from the electric fence to the ground, the current will then flow through them (losing electric potential as it flows "downstream"), and then through the voltage source and electric fence (gaining electric potential as it flows from the low potential (-) to the high potential (+) end), such that the voltage produced by the electric fence is exactly equal to the voltage lost as it current flows through the line of people. (Note that this is a simple current loop, as there are no junctions, such that according to Kirchhoff's junction rule the same amount of current is passing through each of these people!) In lecture we will look at examples of more complicated electrical circuits to analyze using Kirchhoff's rules.