20150427

Online reading assignment: radioactive decay rates

Physics 205B, spring semester 2015
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 radioactive decay rates.


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.
"What equations to use to determine radioactive decay, and what half-life is and how it could be use to find the 'age' of a material."

"How the nucleus of certain elements is unstable and cannot hold together. The idea that this happens at a half-life rate is an idea that I am familiar with. That is about it, I want to know more."

"The older the sample, the more daughter atoms it has. Releasing the daughter atoms when the sample is melted is how you determine the age of the material."

"We are finding the probability of decay over time. The decay of nuclei are indepenant of one another. If we use a short time then we can assume that N (nuclei) is constant. Rate decays also do so exponentially."

"From taking a lot of biology classes and pre calculus I have already been 'exposed' to radioactive decay and have worked out different problems relating to radioactive decay before. I also already understand the idea of it tho the equations seem a bit different compared to how I have solved for decay before."

"I havent gotten to the reading just yet."

"M&Ms® make friends."

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.
"I did not find anything particularly confusing."

"I need to read this more throughly in order to understand this section."

"The whole melting reset thing."
"I do not understand the clock diagram included in the blog presentation. I'm confused as to what happens when the number of daughter atoms dwindles in relation to the clock example."

"How are daughter atoms trapped as gas inside the sample instead of released into the air?"

"Nothing seems too confusing about this chapter. I didn't know about the reseting the solidification age and why it worked but now I do so that was pretty cool."

"I found some of the equations for activity confusing. If you could go over exactly how to use those equations in class it would be helpful."

"I haven't gotten to the reading just yet."

"I think I have it just fine."

State the SI units for activity (radioactive decays per time).
"Decays/s."

"τ."

"Bq = 1 decay/second."

"Curie (Ci)."

"Didn't read yet."

For a radioactive decay process, the time constant τ ("average lifetime") is __________ half-life T1/2.
less than.  ******* [7]
equal to.  ************ [12]
greater than.  ****************** [18]
(Unsure/guessing/lost/help!)  **** [4]

Two samples are each comprised of 800 unstable atoms that will undergo radioactive decay. The remainder of one sample is 200 inert, stable atoms not involved in a radioactive decay process. The remainder of the other sample is 200 daughter atoms of the radioactive decay process.
(Only correct responses shown.)
Sample with more activity (decays/time): (there is a tie). [15%]
Sample with older solidification age: adioactive sample with daughter atoms. [28%]

Describe what changes in a sample when it melted and then solidified that resets its solidification age as determined by radioactive dating.
"The gaseous daughter atoms are released while the radioactive atoms are left in the sample."

"I am unsure."

"All the radioactive daughter atoms are released when the substance is melted. Once it solidifies, the substance starts out again with no daughter atoms."

"Its structure."

"The radioactive atoms change into a gaseous form."

"you date things by measuring the gases trapped in a melted. If it is melted then all the gas will escape and leave the melting, reseting it to just non decayed atoms."

"We are concerned with daughter atom counts. A resolidified material has no daughter atoms and is thus considered 'reset' in terms of radioactive dating."

"When a sample is melted all the daughter cells that are trapped in the sample in gaseous form are released and the age of the sample can be determined by the material that is left. The sample is reset without any daughter cells in the sample and sort of resets the age of the sample due to the lack of daughter cells."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Can you explain the concept of solidification?"

"I would not have guessed that radioactivity involves physics." (Damn straight it does.)

"I'm not sure if I really believe in the accuracy of carbon dating, seeing that decay is really a random event." (Yes, on an individual atom-by-atom basis, the event of a decay is randomized, but with a large enough statistical ensemble, the decays that occur match up well with the expected probability.)

"Trying to finish this semester strong and stay motivated in physics." (#livestrong #finishstrong)

20150425

Astronomy quiz question: light passing through a dark nebula

Astronomy 210 Quiz 6, spring semester 2015
Cuesta College, San Luis Obispo, CA

__________ light can be seen from stars behind a dark nebula.
(A) Blue.
(B) Infrared.
(C) Ultraviolet.
(D) Doppler shifted.

Correct answer (highlight to unhide): (B)

Dust particles will scatter shorter wavelength light more than longer wavelengths. Infrared light, which is the longest wavelength light listed here, should be least affected by passing through a dark nebula.

Section 30676
Exam code: quiz06n1iI
(A) : 10 students
(B) : 20 students
(C) : 6 students
(D) : 30students

"Success level": 59% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.48

Astronomy quiz question: blue color of a reflection nebula

Astronomy 210 Quiz 6, spring semester 2015
Cuesta College, San Luis Obispo, CA

A reflection nebula appears to be blue because its dust particles:
(A) absorb red light.
(B) scatter blue light.
(C) emit blue photons.
(D) have cool temperatures.

Correct answer (highlight to unhide): (B)

Very small dust particles will scatter short-wavelength (blue) light in all directions more than scattering longer wavelengths of visible light (all other colors), such that this nebula will appear blue in color.

Section 30676
Exam code: quiz06szLR
(A) : 3 students
(B) : 37 students
(C) : 7 students
(D) : 0 students

Success level: 81% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.46

Astronomy quiz question: hydrostatic equilibrium between fusion and gravity

Astronomy 210 Quiz 6, spring semester 2015
Cuesta College, San Luis Obispo, CA

To maintain a stable size, the sun uses hydrogen fusion to counteract:
(A) gravity.
(B) dark matter.
(C) convection currents.
(D) proton-proton repulsion.

Correct answer (highlight to unhide): (A)

Hydrostatic equilibrium demands that pressure and weight must balance in order for the sun to maintain its stable size; this pressure is generated by the energy released from fusion in its core to support the weight of the outer layers of the sun produced by its gravity.

Section 30674
Exam code: quiz06n1iI
(A) : 15 students
(B) : 2 students
(C) : 10 students
(D) : 9 students

Success level: 46% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.47

Section 30676
Exam code: quiz06szLR
(A) : 27 students
(B) : 0 students
(C) : 12 students
(D) : 13 students

Success level: 61% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.69

Astronomy quiz archive: stellar evolution

Astronomy 210 Quiz 6, spring semester 2015
Cuesta College, San Luis Obispo, CA

Section 30674, version 1
Exam code: quiz06n1iI


Section 30674
0- 8.0 :  
8.5-16.0 :   ************* [low = 11.0]
16.5-24.0 :   *********
24.5-32.0 :   *********** [mean = 21.3 +/- 7.3]
32.5-40.0 :   *** [high = 40.0]


Section 30676, version 1
Exam code: quiz06szLR


Section 30676
0- 8.0 :   * [low = 8.0]
8.5-16.0 :   ********
16.5-24.0 :   **********
24.5-32.0 :   **************** [mean = 25.2 +/- 8.2]
32.5-40.0 :   ************ [high = 40.0]

20150424

Online reading assignment: flux laws & devices

Physics 205B, spring semester 2015
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 flux laws and devices.


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.
"We look at flux laws and devices here; proving them using different laws. The first law is Faraday's law which begins with the magnetic flux ΦB. The law states that the electric potential is equal to the number of coils N multiplied by the change in magnetic flux ∆ΦB over the change in time ∆t.

"I honestly do not understand any of this stuff! I know it relates to what we learned Monday and Monday's stuff made sense for the most part but I feel like this is another language! Help!"

"I understand the laws used in the presentation. Lenz's law states that direction of this induced current must 'oppose' the changes in magnetic ΦB."

"The basics of how transformers work: they take oodles of electricity and tone it down so it can actually be used."

"When there is a changing magnetic flux there is a emf. That is Faraday's law. The more coils the more emf."

"The magnetic flux ΦB is the product of the magnetic field magnitude B and the area A. The symbol '⊥' represents the maximum value for magnetic flux ΦB."

"Let's be honest. What I understand is that this stuff is confusing. I could not repeat anything back in confidence just from reading the presentation."

"When the magnetic flux is constant or unchanging the there is no induced emf in the wire loop. I understand that the amount of induced emf can be compounded by the number of coil turns N in the wire loop."

"Magnetic flux relates an area to a magnetic field. The most magnetic flux is achieved when the area is exactly perpendicular to the magnetic field lines."

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.
"I got somewhat confused on how the primary and secondary coils gets mixed up when strength is increasing and decreasing. also, I got a little confused from how primary coil voltage can be so high and secondary too low."

"I am still kind of confused as to what a magnetic flux is exactly and how it relates to generators."

"I'm having trouble understanding when a transformer steps down voltage it actually steps up the current."

"Pretty much everything to be honest, I read the blogs and I like to tell myself that it makes it easier to see it again in class because I don't understand anything while reading."

"I need to see some simple laid-out explanations of what is expected of us in terms of formula usage and some of the basic concepts."

"So magnetic flux is sideways current? Or sideways power? I'm still trying to fully understand what a magnet is and does. Flux, coil, inducing...something? None of it makes logical sense."

"I don't really understand what magnetic flux is? Is this just magnetic force?"

"Faraday's law doesn't seem to click conceptually."

State/describe the symbol used for magnetic flux, and give its SI units.
B represents magnetic flux."

"Funny alien looking symbol."

"Wb, T·m2."

For each situation involving magnetic flux and a wire loop, determine whether or not there would be an induced current in the loop.
(Only correct responses shown.)
Constant zero magnetic flux: no induced current in loop [77%]
Constant non-zero magnetic flux: no induced current in loop. [46%]
Magnetic flux increasing in strength: induced current in loop. [82%]
Magnetic flux decreasing in strength: induced current in loop. [59%]

For an ideal transformer that "steps-down" voltage from its primary coils at 120 V to its secondary coils at 2.1 V, determine what happens to the current and to the power from its primary coils to its secondary coils.
(Only correct responses shown.)
Current: stepped-up (increases). [41%]
Power: no change. [28%]

For an ideal transformer that "steps-up" voltage from its primary coils at 1.5 V to its secondary coils at 220 V, determine what happens to the current and to the power from its primary coils to its secondary coils.
(Only correct responses shown.)
Current: stepped-down (decreases). [38%]
Power: no change. [23%]

Explain why a transformer that has the same number of primary coils and number of secondary coils would not be useful.
"The voltage stays constant."

"Because it would not transform anything, by looking at the equations we can see nothing would change. A transformer not transforming is like a heater not heating."

"There magnetic fields that are generated would be the same. So there would be no step up or down."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"The word 'flux' reminds me of the flux capacitor from the Back to the Future movies."

"Hellllppppppp."

"My mind is all fluxed up."

"Why is this class getting harder?"

20150421

Online reading assignment: the Milky Way (SLO campus)

Astronomy 210, spring semester 2015
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 the Milky Way's shape, size and composition and spiral arm structure and formation.


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.
"That we can see galaxies from far away, but because of where we are, we cant see a whole lot of stars in our own galaxy. Freaky!"

"We have the capability to map out where in our galaxy our solar system is!"

"I really like being able to think that we are in a galaxy we can't see out of even though there are a multitude of them."

"Spiral arms are mostly made up of young massive stars that form and die in the arms and that's why the arms are so bright and beautiful."

"The fact that the Milky Way has a flat disk shape. I would have never pictured the shape to be like that."

"Dark matter, because the concept is intriguing and I love a good mystery."

"Where the word 'Milky Way' had originated from."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"I would like some clarification on dark matter. I understand it's in the outer regions of our galaxy, but it is it something I can place in flask jar and bring back with me?"

"What density waves are, and if they cause anything else to happen."

"I don't really understand how we know about our galaxy. I got the analogy about camping but I don't understand the ways or how we deduce what our galaxy looks like."

"How we know how old our galaxy is."

"Nothing confused me."

"I don't really understand the spiral arm density waves and the PimpStar Rims. If you could go over this and the 'traffic jam' reference in class that would help."

"How they figure out the mass of the galaxy did not make sense to me."

"Where is the Milky Way? I've never seen it, or at least known which set of stars it is."

"I found it confusing how to figure out where we are in the Milky Way. This is because I couldn't understand how they could identify where we where exactly without travelling outside. Now I do understand, though."

In your experience, how much of the "Milky Way" (the band of faint stars across the celestial sphere) have you been able to see in the night sky?
As much as can be seen with the naked eye.  ************* [13]
Not very much.  *************** [15]
Barely seen it.  ********** [10]
(Never been able to see it.)  * [1]
(Unsure/guessing/lost/help!)  * [1]

Using the most powerful light-gathering telescopes in the darkest skies, up to how much of the stars in our entire galaxy can be observed from Earth?
1%.  ********* [9]
5%.  *** [3]
10%.  **************** [16]
50%.  * [1]
100%.  ** [2]
(Unsure/guessing/lost/help!)  ********* [9]

If you did not have access to a mirror while camping, what could you do to find out whether or not you're having a bad hair day?
"Use the reflection of water. Or say screw it, I don't need to impress these bears anyways."

"You could use your phone."

"Ask a friend."

"I've never had a bad hair day."

"Throw it in a bun."

"Shave my head."

"Feel your hair to find out if its messy or not."

"The shadow created by the sun."

Look at PimpStar Rims (*.html) for cars, or MonkeyLectric Rims (*.html) for bikes. Briefly explain how they work.
"The eye perceives a synchronized pattern as the lights move, making our eyes think we are looking at consistent image."

"There's a delay between your eyes and what your brain registers so you perceive the patterns into a single image."

"P-dog should work for Pimp My Ride and put Milky Way spinners on rims!"

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"If we take more quizzes then we have to do we get those extra points or do you just drop the lowest three scores?" (The course policy is that you keep your top five quiz scores, and drop your three lowest/missed quizzes.)
"If you could take a minute or two during class to explain how we came to believe there is a supermassive black hole at the center of the galaxy, and what that means for the death of our galaxy." (No, I will not--I know just as much as you do on that topic (i.e., I read the two pages on the supermassive black hole in the textbook), and because it's basically just factual information, it won't be on the next quiz. And no, the supermassive black hole is not going to kill us.)

"Almost two years ago there was a meteor shower and a couple friends and I drove to the middle of nowhere, where there was no light pollution, to see it. What we didn't expect was to also see the Milky Way. It was one of the most beautiful things I have every seen."

"The H-R diagram pisses me off. Makes no sense. And supernovae of all types are not explained well in the book. You should write an astronomy book, please." (No. Because writing textbooks is a trap.)

"Star Wars or Star Trek? Do not take this question lightly." (#jedihandwave This is not the answer you're looking for. But then again, there's an "epic trailer"  that might answer your question.)
"I'm going to need a little more explanation on persistence of vision and how that relates to our galaxy. P.S. Your bike is boss. No hate."

Online reading assignment: the Milky Way (NC campus)

Astronomy 210, spring semester 2015
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 the Milky Way's shape, size and composition and spiral arm structure and formation.


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 enjoyed learning how astronomers determine the shape of the milky way, and theories to why the arms exist."

"The lantern analogy regarding the shape of the galaxy we're in, and how we can determine that shape by looking at the Milky Way 'strip' across the night sky."

"That dark matter exists even though we don't know what it's made of."

"I found the bad-hair day example very interesting because just the simplicity of it made sense, spiral arms equal good hair and blob equals bad hair! Although I have a buzz cut so I cant really have a bad hair day unless I spontaneously lose my hair."

"That the spiral arms of the galaxy are just an illusion they are continuously being created."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"I am still confused about how and why the spiral arms continue to grow."

"I wasn't that confused with this section. My brain did have a hard time grasping the idea of dark matter."

"Radio wave maps."

"Finding the mass of the galaxy was pretty confusing, the text didn't word it very well."

"I found the PimpStar Rims confusing for two reasons:
  1. Would someone really drive around with something like that because that is just screaming to the world a bad message, and
  2. The way it works is interesting, but I can't quite grasp it, I have an idea but am uncertain."
"Where does dark matter come from and what is it?"

"How much of the Milky Way galaxy can be seen with the naked eye?"

"The spiral arms of galaxies--how they are created and how we know we have 'arms.'"

"The Milky Way kept being referred to as a disk, I'm not quite sure what that meant."

"I kind of got how to tell the distance of stars within the galaxy, but would like to get a bit more clarifying information on this."

In your experience, how much of the "Milky Way" (the band of faint stars across the celestial sphere) have you been able to see in the night sky?
As much as can be seen with the naked eye.  ************* [13]
Not very much.  ********** [10]
Barely seen it.  *** [3]
(Never been able to see it.)  ** [2]
(Unsure/guessing/lost/help!)  ** [2]

Using the most powerful light-gathering telescopes in the darkest skies, up to how much of the stars in our entire galaxy can be observed from Earth?
1%.  ***** [5]
5%.  **** [4]
10%.  ********* [9]
50%.  ******** [8]
100%.  [0]
(Unsure/guessing/lost/help!)  **** [4]

If you did not have access to a mirror while camping, what could you do to find out whether or not you're having a bad hair day?
"Have someone look at your hair for you and tell you how it is."

"Look into a still pond or a pool in a brook."

"I would grab a hair brush and french braid my hair to get it our of my face and stop bothering me."

"Eh, I would just rock it, camping is camping."

"You could look at your shadow on the ground, or feel it with your hands."

Look at PimpStar Rims (*.html) for cars, or MonkeyLectric Rims (*.html) for bikes. Briefly explain how they work.
"The lights cordinate when to turn on and off which when crossing our line of visions creates a pattern."

"Rapidly blinking lights can be coordinated to create patterns when swept across our field of view."

"The faster they spin the eye gets tricked and begins to see it as a still picture or light arrangement."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I always have a signal mirror with me when camping. Actually, if you want a cheap signal mirror just use an old CD. Most signal mirrors have holes in them in which you use to aim at whatever you're signalling. You can use a CD in the same manner."

"How often do you update our overall point totals (grades)?" (After each midterm, and the weekend before the final exam.)

"Where did you get your cool light thingy for your bike?" (It was a Schwinn bike accessory from Target, there are similar kits available online.)

20150420

Online reading assignment: generators

Physics 205B, spring semester 2015
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 what you understand from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically demonstrate your level of understanding.
"That some generators do not have to be reset and keep moving. These are continuous generators."

"How a generator and a motor are essentially the same thing. It all depends on whether it is receiving a rotational input on the shaft or is receiving a current flow to cause it to rotate."

"That a metal rod can become a battery when moving at constant speed. The force on the rod pumps the charge in the rod in order to maintain a constant potential difference."

"Hmmm, every lecture we are getting asked what we 'understand.' The more lectures we delve into, the less I am putting it all together and understanding."
"Still haven't gotten to it. I don't understand anything yet."

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.
"The 'hoop-drag' generator was a little difficult to visualize."

"How you would reset a single-pass generator or what constitutes as resetting."

"How continuous generators work, and how to find the forces."

"I don't quite get the point in having ac over dc, or vice versa."

"How as long as a rod moves through a magnetic field its bottom is negative and its top is positive."

"I still don't understand how to make a bicycle-powered generator to fend off the zombie hordes..."

A metal rod moves to the right along a magnetic field that points into the page. The direction of the magnetic force on (fictitious) positive charges in the rod is:
up ↑.  ********************** [22]
down ↓.  ****** [6]
left ←.  *** [3]
right →.  ***** [5]
into the page ⊗.  [0]
out of the page ⊙.  ** [2]
(No direction, as this quantity is zero.)  [0]
(Unsure/guessing/lost/help!)  **** [4]

A metal rod pivoted at one end rotates counterclockwise in a magnetic field that points out of the page. The direction of the magnetic force on (fictitious) positive charges in the rod is:
in towards the center of rotation.  ****** [6]
out away from the center of rotation  *************** [15]
into the page ⊗.  ***** [5]
out of the page ⊙.  ***** [5]
(No direction, as this quantity is zero.)  *** [3]
(Unsure/guessing/lost/help!)  ******** [8]

Explain what a generator is supposed to "generate."
"The movement of electric charges."

"emf."

"Voltage and current."

"Electrical power."

Explain the meaning of "motional" in the term "motional emf."
"It moves."

"The resulting difference in potential when moving a rod through a magnetic field."

"That the emf is created as long as the object is in motion."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"It seems that there are starting to become more than a couple lectures where this 'flipped classroom' style is not working for me. I'm reading and looking at these lectures and not much is sinking in or clicking. I guess this is just how physics goes. When you're not in love with the subject (but still quite fascinated by it) trying to comprehend how things (electricity and magnets) work is just extra-challenging. #stayfocused #onedayatatime" (At the very least your pre-reading responses let me know exactly what you are stuck on--even if it's on the basic stuff--so I know what key points to hit in the following lecture. #notallwhowanderarelost)

"Speaking of a zombie apocalypse, I am watching The Walking Dead right now and it is pretty much epic :-) Also I got a new German Shepherd today, so I am pretty sure I don't have to worry about zombies anymore."

"Still lost on concepts from this past quiz." (Let's make sure that you get caught up on this before the second midterm. See me after lecture, during office hours (make an appointment if necessary), and/or email me.)

"Can you go over the rotating metal rod? It was confusing."

"Can we go over the equations and possibly ways to remember all of them?" (Meh. The right-hand rules are probably more important.)

20150418

Physics quiz archive: circuits (2)

Physics 205B Quiz 5, spring semester 2015
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz05aL7y



Sections 30882, 30883 results
0- 6 :   * [low = 6]
7-12 :   ****
13-18 :   **********************
19-24 :   ************* [mean = 19.0 +/- 5.5]
25-30 :   ******* [high = 30]

20150417

Astronomy current events question: meteorite clues of planetary formation

Astronomy 210L, spring semester 2015
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!)
Johnny Gibbons, "Beautiful Meteorites Hold Clues to Solar System’s Violent Start" (March 27, 2015)
http://smithsonianscience.org/2015/03/beautiful-meteorites-hold-clues-to-solar-systems-violent-start/
Analysis of __________ minerals by Smithsonian Institute researchers reveal clues about impacts that built up Earth and other terrestrial planets.
(A) meteorite.
(B) Earth's ocean floor.
(C) lunar rock.
(D) martian.
(E) fresh Earth lava.

Correct answer: (A)

Student responses
Sections 30678, 30679, 30680
(A) : 38 students
(B) : 7 students
(C) : 2 students
(D) : 3 students
(E) : 1 student

Astronomy current events question: Cassini revisits Saturn's moons

Astronomy 210L, spring semester 2015
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!)
Preston Dyches, Steve Mullins, "Saturn Spacecraft Returns to the Realm of Icy Moons" (March 30, 2015)
http://www.nasa.gov/jpl/cassini/saturn-spacecraft-returns-to-the-realm-of-icy-moons/index.html
NASA's Cassini spacecraft returns to Saturn's icy moons after spending two years:
(A) rebooting its software.
(B) in hibernation.
(C) orbiting Saturn's north and south poles.
(D) recharging its solar batteries.
(E) traveling through Saturn's rings.

Correct answer: (C)

Student responses
Sections 30678, 30679, 30680
(A) : 4 students
(B) : 2 students
(C) : 34 students
(D) : 1 student
(E) : 9 students

Astronomy current events question: nitrate molecules on Mars

Astronomy 210L, spring semester 2015
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!)
Nancy Neal-Jones, William Steigerwald



, "NASA's Curiosity Rover Finds Biologically Useful Nitrogen on Mars" (March 24, 2015)
http://www.nasa.gov/content/goddard/mars-nitrogen/index.html
NASA's Mars rover Curiosity discovered that Mars had conditions habitable for life in its past, based on gases analyzed from:
(A) polar cap dry ice.
(B) heating up soil samples.
(C) a recent dust storm.
(D) melting permafrost.
(E) volcanic vents.

Correct answer: (B)

Student responses
Sections 30678, 30679, 30680
(A) : 10 students
(B) : 33 students
(C) : 3 students
(D) : 4 students
(E) : 1 student

Online reading assignment: magnetic fields of current-carrying wires and loops

Physics 205B, spring semester 2015
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 magnetic fields of current-carrying wires and loops.


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.
"A source object creates a magnetic field everywhere around it. Which exerts force on test object."

"We use RHR3 for a circular loop of current carrying wire, the direction of your fingers curl in the direction of the current along the wire, and the thumb points in the direction of the magnetic B field. RHR2 and RHR3 are similar but represent different magnitudes on the fingers."

"I understand that wires will have a magnetic loop around them whether they are in a closed loop or not. RHR2 and RHR3 predict directions of magnetic field for both cases."

"After the first day of class this week, along with reading the lecture, I'm starting to get a lot more comfortable using the RHR. I understand that the force is always perpendicular to the magnetic force."

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.
"I had a hard time understanding the RHR2 and RHR3 and how they can be applied to the field model. Also, is the source here the wire? contrary to the test objects section?"

"I'm not sure when magnetic forces are possible. RHR2 and RHR3 are confusing."

"I am finding the right-hand rules extremely confusing and could definitely benefit from more examples in class."

"I need clarification on the RHR2 and RHR3 rules and how they work. Also the similarities and differences between a circular current loop and a solenoid."

"So after last class I understood how to utilize the right-hand rule. However, now I'm lost on how to use the new right hand rules. Could we please go over these two new rules together in class along with a couple practice problems using the two different rules? Thank you!"

"The loops are throwing me for a loop. It's really hard to get a good grasp of what is going on by just reading this. I need oral explanations and examples."

State whether it is possible or not possible for the following pairs of objects to exert magnetic forces on each other.
(Only correct responses shown.)
The ends of two bar magnets: possible [64%]
The end of a bar magnet, and a stationary charge: not possible [36%]
The end of a bar magnet, and a moving charge: possible [72%]
Current flowing through a wire, and a stationary charge: not possible [33%]
Current flowing through a wire, and a moving charge: possible [56%]
Current flowing through a wire, and another wire with current in it: possible [44%]

State/describe the symbol used for the "permeability of free space," and give its SI units.
"μ, (H)(m^-1)."

"'Mu,' henries per meter, or newtons per ampere-squared."

"I am not sure."

"Magnetic field (B)."

"I can't find this."

For the magnetic field created by current in a long straight wire, indicate which right-hand finger(s) point along which directions.
(Only correct responses shown.)
Current I in long straight wire: thumb [77%]
Magnetic field B: curled fingers [77%]

For the magnetic field created by a current in a circular loop of wire, indicate which right-hand finger(s) point along which directions.
(Only correct responses shown.)
Current I in circular loop of wire wire: curled fingers [74%]
Magnetic field B: thumb [74%]

Explain the similarities/differences between a circular current loop, and a solenoid.
"No clue what a solenoid is."

"A solenoid is multiple circular current loops."

"They are similar because they are both loops that have magnetic fields flowing between them. They are different because solenoids are uniform and are long in the middle, while circular current loops are more like rings."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I can testify first-hand the effect of coiling electric leads near one's work while welding. If long leads are coiled near the work, the magnetic field compounds and has undesirable effects on a DC welding arc, causing the arc to wander out of control. One of those things you remember after you have already done it."

"I am having a lot of trouble understanding these chapters and feel like I have a lot of work to do in these next few weeks in order for me to do well. First I need to focus on this quiz we have Friday."

"I'm really confused about the different hand rules/when to use them?"

"Wow, it just keeps getting more and more confusing. You are killing me."

"Need some more explanations!"

"I love bacon." (I love turtles.)

20150415

Online reading assignment: medium-mass stars, massive stars, neutron stars and black holes (SLO campus)

Astronomy 210, spring semester 2015
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 the evolution of medium-mass stars, massive stars, neutron stars and black holes.

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.
"Time dilation and curvature of spacetime, because I just saw interstellar and I could relate to what the slides were talking about it."

"It had not occurred to me that a Hummer could travel as far as a SmartCar, but the answer is almost self-explanatory."

"I honestly found everything about the death of stars super-interesting."

"I like how you compare a star's life with the cars. It really helps to understand things better. At first I thought they would be like cars, to later find out they're nothing like them."

"The lifetime of the stars was interesting because the low mass stars live the longest and none has ever died. I would think the larger stars would live longer."

"I found the Hummer and SmartCar question interesting because it actually made me stop and think."

"Spaghettification."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"I can't seem wrap my head around time dilation."

"I don't understand how two stars can be born at the same time but yet one lives way longer than the other."

"I'm not sure why some stars die faster than other, I get it has to do with mass but I don't understand why."

"The different types of explosions each star makes."

"Black holes."

"I found it confusing how smaller stars live longer. This was confusing because compared to planets, bigger planets' core stays warm longer, making it live longer, so I would have assumed it's the same for stars. Guess not!"

A Hummer H2 and a SmartCar ForTwo can travel the same distance with a full tank of gas. Briefly explain how this is possible.
"The SmartCar has a better mileage per gallon and the hummer has a lower mileage per gallon than the SmartCar. Taking that into consideration, the Hummer can hold a bigger amount of gas that yields a certain amount of mileage traveled. The SmartCar being smaller, can hold less gas, but can travel further per gallon, thus they travel the same distance with a full tank of gas."

"One has a bigger gas tank than the other."

"Because they convert the gas at the same rate."

"I'm still completely lost and need help with this."

Match the end-of-life stage with the corresponding main-sequence star.
(Only correct responses shown.)
Black hole: massive main sequence star [85%]
Neutron star: massive main sequence star [50%]
White dwarf: medium-mass main-sequence star [56%]
(No stellar remnant observed yet: low-mass main-sequence star [47%]

Match the type of explosion (if possible) with the corresponding main-sequence star.
(Only correct responses shown.)
Type II supernova: massive main sequence star: [76%]
Type Ia supernova: medium-mass main-sequence star [79%]
Nova: medium-mass main-sequence star [50%]
Low-mass main-sequence star: (no explosion possible) [53%]

If you were to leap into a black hole, your friends would typically watch you falling in for __________ before you entered the event horizon.
seconds.  **** [4]
hours.  * [1]
days.  * [1]
a year.  [0]
many years.  * [1]
forever.  ********************* [21]
(Unsure/guessing/lost/help!)  ****** [6]

The first rule of astronomy class is...
"'It’s a 'religion for intelligent atheists' (from The Theory of Everything)."

"Bring coffee and a snack."

"Show up with caffeine!"

"To call you 'P-dog.'"

"Reach for the stars!"

"'Be informed of and to abide by all student policies outlined in the Cuesta College Catalog, and deadlines in the Cuesta College Class Schedule.'"

"Everything is astronomy is HUGE."

"There are no stupid questions."

"Stars are the best ever, dont mess with black holes."

"Do your homework so you can pass! :)"

"Sci-fi films are not indicative the actual science behind astronomy."

"Come to class."

"The first rule of astronomy class is you have to like stars."

"Always expect the unexpected?"

"Never be late."

"Respect P-dog."

"I am not sure."

"Expand your knowledge. Make conclusions on scientific observations? I'm not sure."

"Have fun?"

"Don't talk about astronomy class."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Talk about Interstellar and its credibility to be real or not?"

"I don't know what Stephen Hawking is talking about, and I have tried to read his book A Brief History of Time but it;s like eating soup with a fork."

"If your friends leaped into a black hole, would you leap too?" (Hey, someone's gotta watch them fall in.)

"Why do you grade so much more leniently than other teachers? It really makes learning this subject much more interesting! I appreciate it!" (Really? Some other students might have the complete opposite opinion about grading, but still, you're welcome.)

"If one entered a black hole, would their life expectancy grow larger than normal? or shorter?" (From that person's perspective, spaghettification would end their life pretty quickly. From the outside observers' perspective, the spaghettification process would look slowed down.)

"I loved all the visuals for the black holes!"

"Why do we see the sky as blue when space is black?" (The atmosphere scatters short wavelengths (blue) from sunlight. At night, the atmosphere is still there, but there is no sunlight to scatter, so it appears clear.)

"Have you ever watched the movie Event Horizon?" (Yes. I found it interesting because it was a stupid, yet very scary science fiction movie at the same time.)

"I loved all the visuals for the black holes!"

"Whats your favorite part of astronomy?" (This stuff.)

"What did you do for spring break? (Mainly just trying to keep up with Mrs. P-dog.)

20150414

Online reading assignment: medium-mass stars, massive stars, neutron stars and black holes (NC campus)

Astronomy 210, spring semester 2015
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 the evolution of medium-mass stars, massive stars, neutron stars and black holes.


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.
"That something as important to Earth as the sun will end up as white dwarf."

"If you were to leap into a black hole, your watch would tell you it took two months to reach the event horizon. Friends watching you would never see you reach the event horizon."

"I liked looking at the different types of novae. Very cool and pretty."

"That all heavy elements were produced by supernovae."

"For once, nothing seemed interesting. I think that's a bad sign."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"Black holes. I'm not really sure on how they work."

"The example of marbles going down the funnel for black holes. I don't understand how that exactly relates to time dilation."

"Black holes are simply confusing."

"Im still trying to comprehend the Hummer and the SmartCar example. HELP PLEASE!"

"Black holes are confusing like whaaaaaaaat. They trip my mind out."

"The difference between a nova and supernovae."

"How are the pulses of a neutron star pulsar produced?"

A Hummer H2 and a SmartCar ForTwo can travel the same distance with a full tank of gas. Briefly explain how this is possible.
"The SmartCar gets better mileage with a smaller tank, while the Hummer has worse mileage but with a bigger tank, allowing both cars to travel the same distance."

"Not sure yet, still trying to understand."

"Going different speeds."

"I was confused on this part of the reading."

Match the end-of-life stage with the corresponding main-sequence star.
(Only correct responses shown.)
Black hole: massive main sequence star [52%]
Neutron star: massive main sequence star [41%]
White dwarf: medium-mass main-sequence star [33%]
(No stellar remnant observed yet: low-mass main-sequence star [41%]

Match the type of explosion (if possible) with the corresponding main-sequence star.
(Only correct responses shown.)
Type II supernova: massive main sequence star: [74%]
Type Ia supernova: medium-mass main-sequence star [63%]
Nova: medium-mass main-sequence star [22%]
Low-mass main-sequence star: (no explosion possible) [59%]

If you were to leap into a black hole, your friends would typically watch you falling in for __________ before you entered the event horizon.
seconds.  ** [2]
hours.  ** [2]
days.  ** [2]
a year.  [0]
many years.  **** [4]
forever.  ************** [14]
(Unsure/guessing/lost/help!)  *** [3]

The first rule of astronomy class is...
"Never regard Pluto as a planet."

"Call you P-dog!"

"Show up and do the work."

"P-dog is always right no matter what."

"Have someone else jump into the event horizon of a black hole for you."

"Ask for proof of everything."

"Look up!"

"Always talk about astronomy class."

"Don't talk about astronomy class." (4 responses.)

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"What happens to a white dwarf star once it completely cools off?" (It should eventually become a black dwarf once it becomes too cool to emit light. This process, however, would take longer than the age of the universe (so far), so it is merely conjecture at this point.)

"If you could push anyone into a black hole who would it be?" (Matthew McConaughey and TARS. Because if anyone can make it back out, they will. Or maybe only TARS, just to see what it would say.)

"The sun is not massive enough to die the supernova death of massive stars." (So, do you think this is a good or a bad thing?)

"How much of this will be on the test? And is there any special people besides you that I can contact for astronomy help?" (The North County learning center has just found an astronomy tutor--one of my best students from last semester!)

"Where is the nearest planetarium located?" (Did you know that San Luis Obispo High School has their very own planetarium? #wut)

"Just look at all those chickens." (I know--just look at them.)

"What did you do for spring break? (Mainly just trying to keep up with Mrs. P-dog.)

20150413

Online reading assignment: magnets, magnetism, and magnetic forces from fields

Physics 205B, spring semester 2015
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 re-reading textbook chapters and reviewing presentations on magnetism and magnetic forces from fields.


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.
"There are the two models of looking at magnetism; direct and field. With direct, we look at the poles and how two magnets can attract or repel each other depending on how they are oriented to each other. The field model is kind of how it sounds, where magnetic forces resonate out and around the source magnet from the poles N to S."

"In RHR1 the angle between v and F should be 90°. A negative moving charge will have the opposite force direction when given with RHR1."

"Magnetic fields (symbol B) are created by charges in motion (currents). Magnetic fields are force fields like electric fields but the magnetic force only acts on charges in motion."

"A magnetic dipole has both a north pole and a south pole. The field lines created by these poles are always closed loops."

"The force of magnetism is attractive if the ends of the source magnet and test magnet face each other with opposite poles, and they repel each other if the ends of the source magnet and test magnet face each other with similar poles. This is very similar to the electric charges, like charges repel and different charges attract."

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.
"The field model is pretty weird."

"When to use LHR. When to use RHR2."

"Noting was too complicated, but the whole right hand rule stuff would be good to review, which I am sure we will be doing on Monday."

"For once, I think I have a handle on all the equations. But I can't quite visualize the RHR1 and how to use it. Except in a street-fight situation."

"The whole thing with the fingers doesnt make any sense to me. Hopefully we can go over it in class and it will make sense. I just can't grasp how it is supposed to tell us which direction it goes or anything!"

Outside of a bar magnet, magnetic field lines travel from the __________ pole to the __________ pole.
north; south.  ****************************** [30]
south; north.  *** [3]
(Unsure/guessing/lost/help!)  ****** [6]

Inside of a bar magnet, magnetic field lines travel from the __________ pole to the __________ pole.
north; south.  *********** [11]
south; north.  ********************** [22]
(Unsure/guessing/lost/help!)  ****** [6]

State the symbol used for the magnetic field, and the SI units for magnetic field strength.
"B, teslas [T]."

"B is used for the magnetic field, and the SI units for magnetic field strength is newtons."

"B, J/s."

Hungry Dragon.  Crunchy Tiger.  Hungry Dragon.  Crunchy Tiger.
When properly using right-hand rule 1, in general there can be any angle between the v thumb and B finger (depending on the situation). In general, specify the angles between the other fingers used in right-hand rule 1.
(Only correct responses shown.)
B finger and F finger: exactly 90° only [31%]
v finger and F finger: exactly 90° only [38%]

In general, the direction of the force of a magnetic field on a moving charged particle will be along the:
particle's velocity vector.  * [1]
the magnetic field line.  ********************* [21]
(Neither of the above choices.)  ****** [6]
(Unsure/guessing/lost/help!)  *********** [11]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"We're getting into some pretty deep stuff here."

"I'm unsure what B exactly represents. Also, no idea what these hand things mean. Trying to figure it out, but I don't get it."

"Can you go over the right-hand rule? It is very confusing to understand from the images."

"How was your spring break?" (Mainly just trying to keep up with Mrs. P-dog.)

20150412

Astronomy quiz question: comparing absolute magnitudes given apparent magnitudes, distances

Astronomy 210 Quiz 5, spring semester 2015
Cuesta College, San Luis Obispo, CA

The apparent magnitudes and distances of three stars are listed below.
m
apparent
magnitude
d
distance
from Earth
Proxima Centauri +11 1.3 pcs
Gliese 15 +11 3.5 pcs
Struve 2398 +9 3.5 pcs

When placed at 10 parsecs away, the star that appears dimmest is:
(A) Proxima Centauri.
(B) Gliese 15.
(C) Struve 2398.
(D) (There is a tie. )

Correct answer (highlight to unhide): (A)

Proxima Centauri and Gliese 15 both appear to be equally dimmer (m = +11) as seen from their true distances from Earth than Struve 2398, which appears to be the brightest (m = +9). Gliese 15 is the same distance from Earth as Struve 2398, but when both are placed at 10 parsecs away from Earth, Gliese 15 would appear to be dimmer than Struve 2398, meaning that Gliese 15 would have a dimmer absolute magnitude M.

When Proxima Centauri and Gliese 15 are both placed 10 parsecs away from Earth, Proxima Centauri would appear dimmer than Gliese 15, as it would move a further distance back away from Earth.

Thus Proxima Centauri would be dimmest at 10 parsecs away from Earth (and thus have the dimmest absolute magnitude M) than Gliese 15, and Struve 2398 would be brightest at 10 parsecs away from Earth (and thus have the brightest absolute magnitude M).

Section 30674
Exam code: quiz05n36A
(A) : 17 students
(B) : 5 students
(C) : 3 students
(D) : 11 students

Success level: 49% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 1.0

Astronomy quiz question: hottest/coolest star?

Astronomy 210 Quiz 5, spring semester 2015
Cuesta College, San Luis Obispo, CA

[Version 1]
Which star is the hottest?
(A) F5 supergiant.
(B) A0 main-sequence star.
(C) M0 red dwarf.
(D) B5 white dwarf.
(E) (There is a tie.)

Correct answer (highlight to unhide): (D)

Using the OBAFGKM spectral type mnemonic, or reading off of an H-R diagram (provided on this quiz, as below), the B5 white dwarf is the hottest star, followed by the A0 main-sequence star, F5 supergiant, and the M0 red dwarf is the coolest.

Section 30674
Exam code: quiz05n36A
(A) : 5 students
(B) : 3 students
(C) : 0 students
(D) : 27 students
(E) : 1 student

Success level: 77% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.70

[Version 2]
Which star is the coolest?
(A) F5 supergiant.
(B) A0 main-sequence star.
(C) M0 red dwarf.
(D) B5 white dwarf.
(E) (There is a tie.)

Correct answer (highlight to unhide): (C)

Section 30676
Exam code: quiz05sOn6
(A) : 0 students
(B) : 1 student
(C) : 39 students
(D) : 5 students
(E) : 1 student

Success level: 85% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.33

20150405

Astronomy quiz question: comparative surface dating of Mercury's surface

Astronomy 210 Quiz 4, spring semester 2015
Cuesta College, San Luis Obispo, CA

Compared to the oldest surfaces on Mercury, the more recently developed surfaces have __________ craters.
(A) fewer.
(B) volcanic.
(C) darker.
(D) collapsed.

Correct answer (highlight to unhide): (A)

Because of the rate of bombardment in the solar system has decreased over time, the density of impact craters indicates the surface age of a terrestrial planet, where a heavily cratered region is relatively older than a region with fewer craters, which would have experienced more recent geological activity that would remove/cover craters.

Section 36074
Exam code: quiz04NoR3
(A) : 26 students
(B) : 5 students
(C) : 4 students
(D) : 3 students

Success level: 71% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.60

Section 30676
Exam code: quiz04s0U7
(A) : 37 students
(B) : 1 student
(C) : 3 students
(D) : 5 students

Success level: 80% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.54

Astronomy quiz question: possible dwarf planet IAU classification of Chariklo

Astronomy 210 Quiz 4, spring semester 2015
Cuesta College, San Luis Obispo, CA

Refer below to the minimal qualifications established by the International Astronomical Union for a planet:
I. Orbits the sun.
II. Shape "rounded-out" by gravity.
III. Cleared/dominates orbit around sun.
Chariklo is an object with an unstable orbit around the sun that passes close to Uranus' orbit[*], and as of March 2015 is listed as a "possible" dwarf planet.[**] In order to officially qualify as a dwarf planet, Chariklo's __________ must be confirmed.
(A) rounded shape.
(B) orbital stability.
(C) influence on solar system debris.
(D) (None of the above choices would confirm Chariklo as a dwarf planet.)

[*] wki.pe/10199_Chariklo.
[**] web.gps.caltech.edu/~mbrown/dps.html.

Correct answer (highlight to unhide): (A)

Chariklo orbits the sun directly, so it is not a moon. If it were irregular in shape, it would classified as solar system debris. However, if Chariklo were rounded in shape, it would then be classified as a dwarf planet (as it does not dominate its orbit around the sun.)

Section 30674
Exam code: quiz04NoR3
(A) : 24 students
(B) : 9 students
(C) : 3 students
(D) : 2 students

Success level: 65% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.25

Astronomy quiz question: possible dwarf planet IAU classification of Chiron

Astronomy 210 Quiz 4, spring semester 2015
Cuesta College, San Luis Obispo, CA

Refer below to the minimal qualifications established by the International Astronomical Union for a planet:
I. Orbits the sun.
II. Shape "rounded-out" by gravity.
III. Cleared/dominates orbit around sun.
Chiron is an object with an unstable orbit around the sun that passes close to Jupiter's and Uranus' orbit[*], and as of March 2015 is listed as a "possible" dwarf planet.[**] In order to officially qualify as a dwarf planet, Chiron's __________ must be confirmed.
(A) rounded shape.
(B) orbital stability.
(C) influence on solar system debris.
(D) (None of the above choices would confirm Chiron as a dwarf planet.)

[*] http://en.wikipedia.org/wiki/2060_Chiron.
[**] http://web.gps.caltech.edu/~mbrown/dps.html.

Correct answer (highlight to unhide): (A)

Chiron orbits the sun directly, so it is not a moon. If it were irregular in shape, it would classified as solar system debris. However, if Chiron were rounded in shape, it would then be classified as a dwarf planet, as it does not dominate its orbit around the sun.)

Section 30676
Exam code: quiz04s0U7
(A) : 29 students
(B) : 14 students
(C) : 3 students
(D) : 1 student

Success level: 64% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.46

20150403

Physics quiz archive: capacitors, circuits

Physics 205B Quiz 4, spring semester 2015
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz04sm7H



Sections 30882, 30883 results
0- 6 :   ****** [low = 0]
7-12 :   *********
13-18 :   **************** [mean = 15.4 +/- 7.0]
19-24 :   ***********
25-30 :   ** [high = 30]

Astronomy quiz archive: sun/spectra/star properties

Astronomy 210 Quiz 5, fall semester 2015
Cuesta College, San Luis Obispo, CA

Section 30674, version 1
Exam code: quiz05n36A


Section 30674
0- 8.0   :
8.5-16.0 :   ******* [low = 12.0]
16.5-24.0 :   ******
24.5-32.0 :   ******* [mean = 27.3 +/- 8.5]
32.5-40.0 :   **************** [high = 40.0]


Section 30676, version 1
Exam code: quiz05sOn6


Section 30676
0- 8.0 :  
8.5-16.0 :   *** [low = 10.0]
16.5-24.0 :   *********
24.5-32.0 :   ****************** [mean = 28.0 +/- 6.6]
32.5-40.0 :   **************** [high = 36.5]

Astronomy current events question: new Milky Way dwarf galaxies

Astronomy 210L, spring semester 2015
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!)
Sarah Collins



, "Welcome to the Neighbourhood: New Dwarf Galaxies Discovered in Orbit around the Milky Way" (March 19, 2015)
http://www.cam.ac.uk/research/news/welcome-to-the-neighbourhood-new-dwarf-galaxies-discovered-in-orbit-around-the-milky-way
Images from the Dark Energy Survey camera revealed nine new __________ orbiting the Milky Way.
(A) potentially Earth-like planets.
(B) black holes.
(C) dwarf satellite galaxies.
(D) dark energy clouds.
(E) spiral arms.

Correct answer: (C)

Student responses
Sections 30678, 30679, 30680
(A) : 2 students
(B) : 2 students
(C) : 38 students
(D) : 6 students
(E) : 3 students

Astronomy current events question: supernova "dust factory"

Astronomy 210L, spring semester 2015
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!)
Blaine Friedlander



, "Milky Way's Center Unveils Supernova 'Dust Factory'" (March 19, 2015)
http://www.news.cornell.edu/stories/2015/03/milky-ways-center-unveils-supernova-dust-factory
The Stratospheric Observatory for Infrared Astronomy (SOFIA) airplane-mounted telescope made direct observations of __________ produced by an ancient supernova.
(A) dust.
(B) hydrogen.
(C) space-time.
(D) dark energy.
(E) gravitational waves.

Correct answer: (A)

Student responses
Sections 30678, 30679, 30680
(A) : 23 students
(B) : 10 students
(C) : 1 student
(D) : 4 students
(E) : 3 students

Astronomy current events question: Comet 67P/Churyumov-Gerasimenko molecular nitrogen

Astronomy 210L, spring semester 2015
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!)
Markus Bauer




, Martin Rubin, Kathrin Altwegg
 and Matt Taylor



, "Rosetta Makes First Detection of Molecular Nitrogen at a Comet" (March 19, 2015)
http://www.esa.int/Our_Activities/Space_Science/Rosetta/Rosetta_makes_first_detection_of_molecular_nitrogen_at_a_comet
Nitrogen molecules from Comet 67P/Churyumov-Gerasimenko detected by the European Space Agency's Rosetta spacecraft indicate that it may have formed:
(A) with polar ice caps.
(B) from a large impact.
(C) within Saturn's rings.
(D) by ancient supernovae.
(E) in the outer solar system.

Correct answer: (E)

Student responses
Sections 30678, 30679, 30680
(A) : 12 students
(B) : 1 student
(C) : 4 students
(D) : 13 students
(E) : 23 students

Online reading assignment: advanced electricity (review)

Physics 205B, spring semester 2015
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 re-reading textbook chapters and reviewing 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.
"Isn't this the same reading assignment? I understand basically everything except when you were talking about that circuit last time in class."

"A fuse is put in series with the circuit and is designed to melt—due to I2R heating—if the current to the circuit exceeds a given value. The melted fuse is an open switch, interrupting the circuit and stopping the current."

"I understand Kirchhoff's rules a lot better, but I think the labs are really helping me understand all of this cause I feel like electrical stuff really isn't my strong point."

"'Joule heating' is the historical term for the power (or rate of energy used per time) continuously used by a circuit element of resistance R due to the amount of current I flowing through it, as in those radiating coils."

"I understand that ammeters must be wired in series while voltmeters must be set up in parallel. If ammeters are wired in parallel the current will take the path of least resistance (zero for an ideal ammeter) instead of going through the resistor which would result in a dangerous amount of current in the circuit. If a voltmeter is wired in series no current can flow through the circuit due to its infinitely high resistance that would zero out the current. The remaining voltage would be a useless reading."

"'Twinkle twinkle little star, power equals I squared r."

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.
"I had some difficultly understanding the loop rule."

"I found power confusing. Wiring both voltmeters and ammeters seems tricky still."

"I get confused with the difference between voltage and current. I don't understand (yet) how to read or figure out electric potential differences. It felt like in lab you could get different readings depending on where you put the leads, but I'm not sure.'

"The most confusing part of the readings and also apart of the labs is understanding how the ammeters, ohmmeters and voltmeters are used unless they are first explained to me."

"I'm confused by the law for circuits and what it is actually used for and how to manipulate the variables."

"I'm not exactly sure how runaway currents work. Additionally I dont understand how the circuit breaker is implemented to prevent runaway currents."

"I still get confused with electric potential, electrical potential energy, wells and peaks, and the direction of decreasing and increasing values based on the sign of the charge. I also get confused when reducing circuits to find total current and then building them back up again and applying the rules of a circuit in series versus a circuit in parallel. Especially with the more confusing circuit arrangements."

What are the resistances of these (ideal) devices?
(Only correct responses shown.)
Ideal light bulb: some finite value between 0 and ∞ [61%]
Burnt-out light bulb: ∞ [37%]
Ideal wire: 0 [48%]
Ideal (non-dead) battery: 0 [45%]
Real (non-dead) battery: some finite value between 0 and ∞ [61%]
Ideal switch, when open: ∞ [42%]
Ideal switch, when closed: 0 [42%]

Two light bulbs with different resistances r and R, where r < R, are connected in series with each other to an ideal emf source. Select the light bulb with the greater quantity.
(Only correct responses shown.)
More current flowing through it: (there is a tie) [42%]
Larger potential potential difference: light bulb R [45%]
More power used: light bulb R [34%]

Two light bulbs with different resistances r and R, where r < R, are connected in parallel with each other to an ideal emf source. Select the light bulb with the greater quantity.
(Only correct responses shown.)
More current flowing through it: light bulb r [50%]
Larger potential potential difference: (there is a tie) [26%]
More power used: light bulb r [32%]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"If I was in prison, I would just study physics all day." (No better way to get pumped up.)

"Will try not to forget this over spring break."

"I think I need an intervention on this conceptual stuff and resistances for real versus ideal devices."

"It all seems simple enough, until it gets confusing."