Physics quiz question: power dissipated by resistor in parallel circuit

Physics 205B Quiz 5, spring semester 2018
Cuesta College, San Luis Obispo, CA

An ideal 6.0 V emf source is connected to a resistor and two light bulbs. The electrical power used by the 4.0 Ω resistor is:
(A) 1.5 W.
(B) 9.0 W.
(C) 24 W.
(D) 96 W.

Correct answer (highlight to unhide): (B)

The basic equation for the power dissipated by the 4.0 Ω resistor is:

P_resistor = I_resistor·ΔV_resistor,

where the current through the resistor I_resistor is not equal to the current passing through the 6.0 V emf source (I_circuit = ΔV_resistor/R_eq), due to the junction rule. However, we do not need to find I_resistor, as we can appeal to Ohm's law:

I_resistor = ΔV_resistor/R_resistor,

such that we can substitute this into the basic power equation, and result in a "specialized" form of the power equation for this resistor:

P_resistor = I_resistor·ΔV_resistor,

P_resistor = (ΔV_resistor/R_resistor)·ΔV_resistor,

P_resistor = (ΔV_resistor)²/R_resistor.

To find the ΔV_resistor voltage used by the resistor, we apply the loop rule in the clockwise direction, starting from lower right-hand corner, through the 6.0 V emf source, then through the 4.0 Ω resistor before returning to the starting point in the lower right-hand corner (the loop rule can be applied to any round-trip loop in a circuit, even if there are other parts of this circuit):

"voltage supplied = voltage used,"

∆V_rises = ∆V_drops,

(6.0 V) = ΔV_resistor.

Then we can evaluate the "specialized" form for the power used by the resistor:

P_resistor = (ΔV_resistor)²/R_resistor,

P_resistor = (6.0 V)²/(4.0 Ω) = 9.0 W.

(This "specialized" equation for power should only be used if the voltage used by the circuit element is known already either from the loop rule (as was done here) or from Ohm's law.)

(Response (A) is the numerical value for the current flowing through the resistor; response (C) is ΔV_resistor·R_resistor; response (D) is ΔV_resistor)²·(R_resistor)².)

Sections 30882, 30883
Exam code: quiz05z0m6
(A) : 5 students
(B) : 19 students
(C) : 9 students
(D) : 1 student

Success level: 56%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.83

Physics quiz question: equivalent resistance of serio-parallel circuit

Physics 205B Quiz 5, spring semester 2013
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Comprehensive Problem 18.112

An ideal 12 V emf source is connected to three resistors, as shown at right. The equivalent resistance of this circuit 
is:
(A) 3.4 Ω.
(B) 4.7 Ω.
(C) 9.3 Ω.
(D) 14.0 Ω.

Correct answer: (C)

The 2.0 Ω resistor and the 4.0 Ω resistor are directly connected in parallel to each other, such that their equivalent resistance is:

R_2,4 = [ (R₂)^–1 + (R₄)^–1 ]^–1,

R_2,4 = [ (2.0 Ω)^–1 + (4.0 Ω)^–1 ]^–1,

R_2,4 = 1.333... Ω.

Then the 8.0 Ω resistor is in series with the combined R_2,4 equivalent resistor, so the final equivalent resistance of the circuit is:

R_eq = R₈ + R_2,4,

R_eq = 8.0 Ω + 1.333... Ω = 9.3 Ω, to the significant tenths decimal place.

(Response (A) is where the 2.0 Ω resistor and the 4.0 Ω resistor are first combined in series, and their resulting equivalent resistance R_2,4 combined in parallel with the 8.0 Ω resistor; response (B) is the average of all three resistance values; response (D) is the sum of all three resistance values.)

Section 30882
Exam code: quiz04eQu7
(A) : 1 student
(B) : 4 students
(C) : 25 students
(D) : 2 students

Success level: 80%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.38

Online reading assignment: Kirchhoff's laws (SLO campus)

Astronomy 210, spring semester 2020
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 Kirchhoff's laws.


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 it interesting that the emission spectrum relates to the material we learned in class a few weeks ago about gaseous elements. Before, I was only aware that particular colors of light are exclusively emitted depending on the movement of electrons in an element. However, I now know light can be emitted as also a continuous or emission spectrum. I found this interesting because it did not occur to me that a star or even a rainbow might emit photons differently due to their specific spectrum types."

"I find the different spectra interesting. It interests me to know how different things put out different types of light and to learn the science behind it. I always knew that neon lights were different from normal lights, but understanding how they produce their colors is an experience!"

"The spectrum types are very interesting, albeit confusing, from reading about it on my own. It seems like something that will take some further explanation and repetition to get down, but I am interested in exploring it further as light is all around us."

"I enjoyed learning about the different spectra and what produces them. I only knew about the continuous spectrum, so learning about the other ones was very interesting."

"Something I found interesting was the spectra of the sun and stars. This was interesting to me because I didn't know how the spectra was made, and the process is very intriguing."

"I have always found the Doppler effect super-interesting. It is just such an interesting and curious effect. After reading this, it makes a lot more sense."

"The Doppler effect is interesting to me because you can interact and hear it everyday. I think it's really cool that a pitch of sound is determined by its wavelength."

"I really liked learning about the Doppler effect. I never really paid attention to the different pitches a horn makes as it is moving past someone. I think it is interesting that it changes depending on if the car is moving towards you or away from you."

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

"I have a good understanding on the three different types of light spectrum; however, I seem to be struggling with correlating them to actual pictures of objects. When they are shown in the boxed diagrams it is easier to distinguish them, but I'm not sure how to transfer that over to real-life objects."

"I was having a little difficulty debating which things went with emission and absorption spectra, I think I might be getting them backwards, but I also might be right! Lol"

"The three kinds of spectra and their rules.It is hard for me to conceptualize things that I have not heard of before."

"The overview of Kirchhoff's laws in the textbook were too brief and vague."

"The blueshifts and redshifts confuse me because I do not understand the definitions given in the textbook."

"I found it interesting to learn about the Doppler effect but it was more difficult for me to understand. Seeing the wavelengths that a car sound makes when driving past you helped me better understand it since it was drawn out."

I believe Pluto should be a planet. (Original responses.)

Strongly disagree.	* [1]
Disagree.	************ [12]
Neutral.	************ [12]
Agree.	******** [8]
Strongly Agree.	* [1]

I believe Pluto should be a planet. (This is a follow-up question.)

Strongly disagree.	**** [4]
Disagree.	************* [13]
Neutral.	********** [10]
Agree.	***** [5]
Strongly Agree.	* [1]

Briefly explain your answer to the previous question (whether Pluto should be a planet).

"I don't disagree nor agree. I find that the neutral position is easier and shows that the decision of planet making is not mine."

"I agree it should be a planet because it has everything other planets have like being round."

"I agree Pluto should be a planet because it has all the same aspects other planets have like being round."

"It doesn't fit the new definition of what a planet is but lots of people who don't know that definition still call it a planet, so I'm fine with either or."

"I know now that Pluto should not be a planet. It just doesn't fit the criteria."

"I don't really have a strong opinion on whether Pluto should be a planet or not, but based off the evidence it doesn't seem like Pluto fits into the 'planet' category to well. Pluto's orbit and size differ a lot from all of the other planets, it really doesn't seem to fit in."

"After learning the guidelines for what constitutes a planet, it is clear that Pluto does not qualify as one. Though, I don't feel to strongly about it, I wouldn't mind seeing it make a comeback, though that would require a lot of changes in planet definitions."

"I'm neutral. I grew up knowing Pluto was a planet and then became a star, so for me Pluto will always be a planet at heart."

"I believe that if we found life or movement on Pluto we could possibly consider looking into it becoming a planet. However, like I previously said Pluto shouldn't become a planet because its not in the orbiting rings."

"I believe that if we found life or movement on Pluto we could maybe consider looking into it becoming a planet. However, like I previously said Pluto shouldn't become a planet because its not in the orbiting rings."

"Due to it being a body that orbits the sun and it's a dwarf planet."

"I understand why Pluto is no longer considered a planet, because it doesn't dominate its orbit, but since I grew up thinking it was a planet, it is hard for me to view it as anything different. it doesn't fit under the standards of being a planet after learning it doesn't dominate its orbit."

"Pluto should not be a planet because there is many other similar sized dwarf planets in the Kuiper belt that are not considered planets either."

"I do not think it's a planet. But I’m still neutral because I'm willing to listen to someone's views on why it is one."

"Pluto doesn't dominate its orbit so it can’t be a planet. Based off the three classifications for being a planet, Pluto meets all 3. It should be considered a planet, no matter how small it is."

"If Pluto could be a planet then so many others could be too. We would be back in a time with 1,500+ planets and more discovery would lead to more and more. Having a three-step classification narrows down the most important ones to watch."

"Since it was once a planet, I think that it should always be a planet. Although it is known as the dwarf planet, when I first learned about planets it was there, so I will always think it is still considered a planet."

"I don't believe that Pluto should be a planet, and redefining it as a dwarf planet was the correct choice. If it dominated its own orbit around the sun, and didn't come in so close to the moon, and then further than anything else."

"Pluto is too small and boring."

"According to the classifications that we learned about, it doesn't make sense to treat it as a planet."

"Pluto had a good run, we should give Makemake a chance at planethood."

"The classifications makes it a dwarf planet due to it not dominating its orbit."

"I believe Pluto should be a planet because it's more of a planet than Jupiter."

"I still do not believe Pluto should be considered a planet because it cannot expel objects from its own orbit. I believe this fact alone is convincing because asteroids are not considered planets for the same reason. All objects in space must be evaluated with the same set of IAU rules, meaning Pluto's failure to meet these criteria technically would imply it is not a planet."

"Well, I now know how planets are categorized and by following that Pluto is a dwarf planet."

"Pluto can't be a planet, because it does not dominate its own orbit. It fits all the other qualifications for being a planet, except for the fact that it doesn't dominate its own orbit. Therefore, it is considered a dwarf planet."

"The rules are too strict for being a planet."

"Pluto should not be a planet because it does not dominate its orbit, therefore it should be a dwarf planet based on the IAU classes and rules."

"I don't have much of a preference because the logical part of me sees why it's a dwarf planet because it doesn't hit all the criteria of being an independent planet but there's also a part of me that wants Pluto to belong with the other major planets in our system since the little guy is so far away and is already isolated."

Match the spectrum type with their appearance.
(Only correct responses shown.)

Rainbow containing all colors: continuous [85%]
Rainbow with thin black lines: absorption [76%]
Colored lines on a black background: emission [79%]
Given off by hot, dense object: continuous [70%]
Given off by hot, diffuse gas atoms: emission [67%]
Passing through cool, diffuse gas atoms: [52%]

Hot, molten metal produces a(n) __________ spectrum, which appears as a:

continuous; rainbow.	********** [10]
emission; series of bright lines on a dark background.	******* [7]
absorption; series of dark lines on a rainbow background.	********* [9]
(Unsure/guessing/lost/help!)	******* [7]

The sun produces a(n) __________ spectrum, which appears as a:

continuous; rainbow.	******** [8]
emission; series of bright lines on a dark background.	******* [7]
absorption; series of dark lines on a rainbow background.	************* [13]
(Unsure/guessing/lost/help!)	***** [5]

The lights atop the Fremont Theater in San Luis Obispo, CA, produces a(n) __________ spectrum, which appears as a:

continuous; rainbow.	*********** [11]
emission; series of bright lines on a dark background.	************** [14]
absorption; series of dark lines on a rainbow background.	****** [6]
(Unsure/guessing/lost/help!)	** [2]

Your instructor produces a(n) __________ spectrum, which appears as a:

continuous; rainbow.	******* [7]
emission; series of bright lines on a dark background.	*************** [15]
absorption; series of dark lines on a rainbow background.	*** [3]
(Unsure/guessing/lost/help!)	******** [8]

The balrog from The Lord Of The Rings: The Fellowship Of The Ring produces a(n) __________ spectrum, which appears as a:

continuous; rainbow.	*** [3]
emission; series of bright lines on a dark background.	***************** [17]
absorption; series of dark lines on a rainbow background.	**** [4]
(Unsure/guessing/lost/help!)	********* [9]

Suppose you are standing on the sidewalk as a car, with its horn continuously on, passes by (video link). The loudness of the car horn:

starts loud, then gets quieter.	**** [4]
starts quiet, then gets louder.	***** [5]
starts quiet, gets louder, then goes back down to quiet.	*********************** [23]
starts loud, gets quieter, then goes back up to loud.	[0]
(Unsure/guessing/lost/help!)	* [1]

Suppose you are standing on the sidewalk as a car, with its horn continuously on, passes by (video link, same as above). The pitch (high note/low note) of the car horn:

starts high, then drops lower.	************* [13]
starts low, then goes higher.	**** [4]
starts low, goes higher, then drops back down to low.	************ [12]
starts high, goes lower, then goes back up to high.	*** [3]
(Unsure/guessing/lost/help!)	* [1]

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

"The spectrum picto-quiz was a bit challenging for me, can we find a way to go over these?"

"How do you differentiate between the different spectrums in terms of the examples that were given? I guess I'm still a little confused about their real-life applications and how each works."

"I was hoping you could provide a little more clarification on distinguishing what spectrum is being seen. I had trouble figuring out the ones that were different from the exact examples given when explaining what produces what spectra."

"I'm concerned on how learning the material more on my own will be with it all being online because the lectures were the most helpful with making me understand material."

"Are you happy going completely online? Do you think there is a chance of us maybe coming back to school if this all clears beforehand? I do NOT like all online at all." (I'm okay with it, but it is a lot of work (but I'm finally getting around to learning how to use Adobe Premiere Pro, which I've always wanted to do). As much as I would like us to return back to face-to-face classes before the end of this semester, I'm rather pessimistic about that happening.)

"Online is going to be different, but good." (I appreciate your optimism.)

"Have you ever taught this course online before? Pros and cons?" (No, this is my very first time. I'm having to learn a lot very quickly, it reminds me of when I first started teaching at Cuesta College.)

"I don't know if I'll be fine in an online class since I learn more face-to-face when you explain these things to us."

"I really appreciate the option of 'unsure/lost/guessing/help' on these questions, and I think its a fair choice for assignments like this. However, I think students have the tendency to guess an answer instead of choosing 'unsure/lost/guessing/help' in order to greatly increase their chances of getting lucky and getting points. This is just something that crossed my mind. I know you appreciate knowing if students genuinely don't understand a question or concept, so I am just wondering if this tendency might skew the feedback." (Everyone gets credit for answering a question, whether they get it correct, incorrect, or choose 'unsure/lost/guessing/help.' I think choosing 'unsure/lost/guessing/help' is actually a very honest way of students letting me know that we need to focus on certain topics in class.)

"Will there still be a tutor available for this class now that it is fully online?" (I've asked about that; still waiting to hear from the Student Success Center if tutors will be available online.)

"Thank you for your work in this difficult time." (You're welcome. Thank you all for being patient and willing to change over to learning online.)

"I hope you are staying healthy!" (You, too! #socialdistancing)

"Do you use Spectrum internet?" (Ironically, yes.)

Online reading assignment: Kirchhoff's laws (NC campus)

Astronomy 210, spring semester 2020
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 Kirchhoff's laws.


Selected/edited responses are given below.

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

"How heat can be measured by color. This was interesting to me because you only really think of 'red-hot.' Not much about any other colors."

"This was a rather confusing chapter..."

"The assigned textbook reading was interesting to me because I didn't understand the different forms of light before. I think it's interesting how there is a continuous spectrum, absorption spectrum, and an emission spectrum. I learned something new about light and it was interesting."

"Something I found out that was really interesting to me that I learned from the reading was the Doppler effect for sound and light. It was interesting learning that longer wave lenghths have low pitches and shorter wavelengths have higher pitches, and vice versa with light having the blueshift refer to shorter wavelengths of light and a redshift with longer light wavelengths."

"To learn why car horns sound different when they come towards you and pass you. It's something you don’t really think about much."

"I found the Doppler effect on light from stars interesting, I never knew the way they were moving affected the way we see them."

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

"I didn’t really understand how stars and absorption relate to each other. I know that they start with continuous light from the center but that's where I stopped understanding."

"The Doppler effect, the explanation in the textbook was hard to follow."

"I originally found the stuff on the spectra confusing, because I had trouble distinguishing between the different types at first, but now I think I know them all."

"I do not understand how to really tell the different spectra of light-producing objects. I do not know what I am really looking for."

"Colors in general are hard for me to grasp. Being color deficient makes this lesson hard to learn visually."

I believe Pluto should be a planet. (Original responses.)

Strongly disagree.	*** [3]
Disagree.	******* [7]
Neutral.	********** [10]
Agree.	***** [5]
Strongly Agree.	*** [3]

I believe Pluto should be a planet. (This is a follow-up question.)

Strongly disagree.	* [1]
Disagree.	******** [8]
Neutral.	***** [5]
Agree.	** [2]
Strongly Agree.	[0]

Briefly explain your answer to the previous question (whether Pluto should be a planet).

"It has been considered a planet but I don’t think it really matters if it is or isn't."

"I still believe that Pluto should not be a planet. The IAU had a definition of planets that was too loose and Pluto doesn't fit the criteria."

"It doesn't dominate it's orbit, and it's smaller than our own moon. Pluto does have moons which I think makes a pretty good case for it, but not having enough mass to dominate it's orbit is important in hindsight."

"I don't feel any particular way. As long as we continue to study the planets and make scientific progress."

"I have no strong opinion."

"I don't think that Pluto should be a planet because it doesn't follow the guidelines to be considered a planet."

"The way they classify a planet is very sound."

"I think that Pluto still deserves to have the label as a planet because I think it would be a really cool planet to have in a solar system and it has all the qualities a planet needs besides being in charge of its own orbit."

"I don't feel as strongly that Pluto needs to be a planet. In addition, I agree that we needed better, standardized methods for organizing what is and isn't a planet."

"Now that I learned what defines a planet I now understand Pluto doesn't classify since it does not dominate its orbit."

"I know that Pluto does not classify as a planet with the new rules. But there is still some satisfaction/niceness to still calling Pluto a planet"

"It doesn't meet the criteria to be a planet."

"Due to the newer definition of what a planet is, Pluto just doesn't qualify, it doesn't dominate its orbit 3/14/2020"

"I'm still neutral because it honestly doesn’t matter to me. I understand why it's a dwarf planet now with it sharing its orbit but it doesn’t matter to me if Pluto is a planet or not."

"Pluto does not meet the criteria to classify as a normal planet because it does not clear its orbit."

Match the spectrum type with their appearance.
(Only correct responses shown.)

Rainbow containing all colors: continuous [94%]
Rainbow with thin black lines: absorption [75%]
Colored lines on a black background: emission [69%]
Given off by hot, dense object: continuous [75%]
Given off by hot, diffuse gas atoms: emission [75%]
Passing through cool, diffuse gas atoms: [75%]

Hot, molten metal produces a(n) __________ spectrum, which appears as a:

continuous; rainbow.	********** [10]
emission; series of bright lines on a dark background.	** [2]
absorption; series of dark lines on a rainbow background.	*[1]
(Unsure/guessing/lost/help!)	*** [3]

The sun produces a(n) __________ spectrum, which appears as a:

continuous; rainbow.	* [1]
emission; series of bright lines on a dark background.	****** [6]
absorption; series of dark lines on a rainbow background.	******** [8]
(Unsure/guessing/lost/help!)	* [1]

The lights atop the Fremont Theater in San Luis Obispo, CA, produces a(n) __________ spectrum, which appears as a:

continuous; rainbow.	**** [4]
emission; series of bright lines on a dark background.	********* [9]
absorption; series of dark lines on a rainbow background.	** [2]
(Unsure/guessing/lost/help!)	* [1]

Your instructor produces a(n) __________ spectrum, which appears as a:

continuous; rainbow.	**** [4]
emission; series of bright lines on a dark background.	******* [7]
absorption; series of dark lines on a rainbow background.	*** [3]
(Unsure/guessing/lost/help!)	** [2]

The balrog from The Lord Of The Rings: The Fellowship Of The Ring produces a(n) __________ spectrum, which appears as a:

continuous; rainbow.	***** [5]
emission; series of bright lines on a dark background.	***** [5]
absorption; series of dark lines on a rainbow background.	** [2]
(Unsure/guessing/lost/help!)	**** [4]

Suppose you are standing on the sidewalk as a car, with its horn continuously on, passes by (video link). The loudness of the car horn:

starts loud, then gets quieter.	** [2]
starts quiet, then gets louder.	** [2]
starts quiet, gets louder, then goes back down to quiet.	*********** [11]
starts loud, gets quieter, then goes back up to loud.	[0]
(Unsure/guessing/lost/help!)	* [1]

Suppose you are standing on the sidewalk as a car, with its horn continuously on, passes by (video link, same as above). The pitch (high note/low note) of the car horn:

starts high, then drops lower.	****** [6]
starts low, then goes higher.	[0]
starts low, goes higher, then drops back down to low.	******* [7]
starts high, goes lower, then goes back up to high.	* [1]
(Unsure/guessing/lost/help!)	** [2]

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

"Do you think that making all classes go online was an overreaction? Like I went to work today, everything is still relatively normal in Paso Robles." (At this point everyone is going to come down with COVID-19; but social distancing is meant to stretch out the number of people who are sick at the same time (instead of letting everyone get sick at the same time). So, social distancing is the new norm, right now, for times like this. #flattenthecurve)

"I'm so lost with this chapter!"

"How do I take real situations measuring color and heat and apply it. All sources seem to be different. Is there a trick?" (I've posted a "spectra survival guide" video lecture on Canvas for that.)

"Will we find out what we got on our midterms online through Canvas since we aren't meeting in class anymore?" (Yes, although you can still see the midterm scores online on the old website.)

"What's your favorite part about space?" (Teaching about it, then watching students "get it.")

"How are we going to do lectures now that we are online and is it for the rest of the semester?" (I'll make videos and provide notes for the lectures, and make them available online on Canvas. All assignments (including a new discussion board) will be on Canvas as well, along with the quizzes and exams.)

"What's a blackbody spectrum and where is it mentioned? I don't remember seeing it." (It's a different name for a continuous spectrum (which is given off by hot, dense objects, which are also known as "blackbodies.")

Astronomy midterm question: Great Square and Big Dipper just after sunset

Astronomy 210 Midterm 1, spring semester 2020
Cuesta College, San Luis Obispo, CA

An online astronomy magazine article describes the positions of the "Great Square" (located between the constellations Andromeda and Pegasus) and the Big Dipper just after sunset:[*]:

After dark now the Great Square [between Andromeda and Pegasus] is declining low in the west, tipped onto one corner. Meanwhile the Big Dipper is creeping up in the northeast, tipped up on its handle.

Discuss a plausible date and time for someone in San Luis Obispo, CA to make this observation of the Great Square and the Big Dipper in the early evening sky. If there is no such plausible date and time, then explain why. Defend your answer by clearly explaining how you used your starwheel to do this, along with any assumptions that you may have made. (Ignore daylight saving time.)

[*] skyandtelescope.com/observing/sky-at-a-glance/.

Solution and grading rubric:

• p:
  Correct. Discussion includes the following:
  1. locates the Great Square and the Big Dipper asterisms on the starwheel, and rotates starwheel such that the Great Square is just above the west horizon, while the Bigger Dipper is near the northeast horizon; and
  2. selects a time that is dark enough to see stars in the early evening (somewhere between 7 PM and 10 PM or so); and
  3. looks up a specific date corresponding to that early evening time.
• r:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. May have selected midnight, sunrise or some other time of night not convincingly "after dark," "just after sunset" or an "early evening" time.
• t:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. May have Great Square near east horizon, and Big Dipper near the west horizon.
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. At least attempts to use starwheel in a systematic manner.
• x:
  Implementation/application of ideas, but credit given for effort rather than merit. Discussion not clearly based on using a starwheel in a systematic manner.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.

Grading distribution:
Section 30674
Exam code: midterm01n7in
p: 21 students
r: 5 students
t: 3 students
v: 1 student
x: 0 students
y: 0 students
z: 0 students

Section 30676
Exam code: midterm01S7wY
p: 27 students
r: 11 students
t: 2 students
v: 3 students
x: 2 students
y: 0 students
z: 0 students

A sample "p" response (from student 2020):

Astronomy midterm question: "sliced" moon rising with coming darkness

Astronomy 210 Midterm 1, spring semester 2020
Cuesta College, San Luis Obispo, CA

The following excerpt describes the rising of a crescent ("sliced") moon around sunset:

Darkness was coming slowly down, a cool cloak draped over them. Soon, a sliced moon began to rise as a wind rose.

Discuss whether or not this description is plausible for an observer in San Luis Obispo, CA, and how you know this. Support your answer using a diagram showing the positions of the sun, moon, Earth, and an observer on Earth.

[*] Mitchell Smith, Moonrise: Book Three of the Snowfall Trilogy, Tom Dougherty Associates (2004), p. 195.

Solution and grading rubric:

• p:
  Correct. Complete diagram (with the sun, moon, and observer on Earth), and discusses one of the following reasons why this description would be implausible:
  1. waxing crescent moon is overhead at 3 PM, and rose six hours earlier at 9 AM; while waning crescent moon is overhead at 9 AM, and rose six hours earlier at 3 AM, such that neither of these crescent phase moons could be rising just after sunset; or
  2. the moon phase that would be rising around/at/after sunset (6 PM) would be the waxing gibbous moon, full moon or waning gibbous moon, such that no crescent phase moon could be rising after sunset.
• r:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Diagram and/or explanation has minor errors.
• t:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Problems with either diagram or discussion.
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. At least attempts to draw a moon phase diagram and apply rise/overhead/set times.
• x:
  Implementation/application of ideas, but credit given for effort rather than merit. Discussion not clearly based on a moon phase diagram.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.

Grading distribution:
Section 30674
Exam code: midterm01n7in
p: 15 students
r: 3 students
t: 4 students
v: 5 students
x: 0 students
y: 0 students
z: 0 students

Section 30676
Exam code: midterm01S7wY
p: 24 students
r: 2 students
t: 5 students
v: 9 students
x: 5 students
y: 0 students
z: 0 students

A sample "p" response (from student 2310):

Astronomy midterm question: Venus setting while Jupiter rising at night?

Astronomy 210 Midterm 1, spring semester 2020
Cuesta College, San Luis Obispo, CA

The following excerpt describes a night where Venus is setting while Jupiter is rising[*]:

Let me try to recall what has happened, the amusing and strange, and sad and terrible scenes witnessed in these last few days. On my first night at sea, I watched Venus slowly sinking into the sea, and Jupiter rising...

Discuss a plausible time (around sunset, midnight, or sunrise) that these two planets would be observed in San Luis Obispo, CA, and how you know this. Support your answer using a diagram showing the positions of the sun, Venus, Jupiter, Earth, and an observer on Earth.

[*] J.C., "Wrecked--A Week on Sable Island," The Canadian Methodist Magazine, vol. XV (January-June 1882), p. 73.

Solution and grading rubric:

• p:
  Complete diagram and reasoning where observer on Earth must be at sunset to watch Venus (in an inner orbit) setting while Jupiter (in an inner orbit) rises in the east.
• r:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Typically diagram and/or supporting argument is contradictory or incomplete.
• t:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Still has Venus in an inner orbit and Jupiter in an outer orbit around the sun.
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Some attempt at diagram(s), but no clear indication of observer/horizon on Earth and/or placement of inner planets. Typically misplaces Venus and Jupiter in their relative inner/outer orbits around the sun, or has Venus and Jupiter orbiting Earth.
• x:
  Implementation/application of ideas, but credit given for effort rather than merit.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.

Grading distribution:
Section 30674
Exam code: midterm01n7in
p: 14 students
r: 1 student
t: 6 students
v: 7 students
x: 1 student
y: 0 students
z: 1 student

Section 30676
Exam code: midterm01S7wY
p: 24 students
r: 0 students
t: 13 students
v: 6 students
x: 2 students
y: 0 students
z: 0 students

A sample "p" response (from student 2000):
Another sample "p" response (from student 2020):
One more sample "p" response (from student 5171):

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

Astronomy 210, spring semester 2020
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.

"Go over my notes and quizzes."

"This doesn't relate to my study methods at all, but I found the main page difficult to look through. It takes me a minute to get used to its format and maneuver around to find the material I need."

"The notes we take in class are easy to remember because of all the drawn-out diagrams."

"Being allowed to form our own groups is very helpful for studying on the midterm because I can work with people who I know and get along with, making discussion of possible answers much easier."

"What doesn’t help is that we don't have a study guide for help."

"I need to have some background noise on. Nothing too loud or too quiet. If it's too quiet I can get tired or get distracted by the smallest noise. Also, I eat something before studying because I can’t focus well if I haven't eaten."

"Remembering those gosh darn moon phase/time charts"

"Flash cards help me most and having someone quiz me harshly days before, not just the night before. Putting away all distractions and going somewhere quiet. It's awkward at first but really helps. Writing down diagrams immediately while it's fresh in your mind will eventually help remember it better which should help massively on the midterm."

"I need help catching up. because I have missed so much. I apologize."

"I find that studying with music personally helps me. I don't fully understand why but I think it's a bit Pavlovian, listing to music that already makes you happy makes the studying nicer."

"When teachers explain and give examples during class time."

"Study with a fresh mind and practice the mid term review questions."

"Something that really helps me study for the midterm are all of the practice tests we did as the in class activities."

"Diagrams and pictures help the most for me. I am a visual learner, so the diagrams we learned in class have especially helped me understand the material. Going over class notes, quiz packets, old quizzes and material in the book also helps out a lot. The old quiz questions and the ones from the packets help review past material learned."

"Using analogies always helps! Especially remembering the ones you came up with."

"I enjoy working with the groups because we can discuss our answers and I can get a better understanding of something I am confused about."

"Flashcards!"

"For me it helps to have some soothing background music playing it helps my brain focus and tune into the information I need to know."

"I focus on trying to spread out my studying and try not to cram everything in the day before."

"Going back through the practice tests to look at all the questions that you had difficulties with."

"Study guides."

"Having the practice packets for the quizzes and giving out the answers to the quizzes so I think you should do the same for the practice packets."

"It really helps to go over the quizzes!"

"Studying the quiz question packets = life saver!"

"The correct answers of the tests help, and something that would really help would be if the quiz question packet answers would be posted as well."

"Doing practice problems."

"I think that you should give us the answers to the quiz question packets so we know what's right and what's wrong because it would be a great studying tool for this midterm and the upcoming ones."

"For me, making flashcards is really helpful. I also like to do all of the practice quiz questions and draw out all of the pictures we have drawn in class."

"I really benefit by drawing out simplified versions of the diagrams again and again. That way when a question comes up, if I don't immediately know the answer, I can draw the diagram and figure it out."

"The past quizzes seem to help but I'll see how I do on the midterm first to see if it was effective."

"The quiz question packets helped me a lot, but sometimes I wasn't sure of the answer or couldn't find it in some cases. It would be helpful to have answer keys or have a condensed study guide for the midterm with an answer key to refer to when stuck."

"Studying on an empty stomach does not help at all and so does looking at my phone constantly."

"It helps to draw the diagrams over and over in the context of different problems."

"Something that doesn't help is trying to overload your brain with too much information too fast."

"Really good notes from class and practice questions! "

"Something that helps while studying for this midterm is making quizlets and practicing those over and over, as well as going to the tutor."

"Flashcards on the various diagrams we drew throughout the first half of the term."

"The focal points in the telescopes are when the lines come together"

"Understanding the notes and questions is way more valuable than trying to understand all of the reading."

"Reviewing lecture slides remind me of helpful analogies."

"I do not find the set-up for the study guides all too helpful. With so much information, I often do not know what to focus on, and get lost."

"Reviewing quizzes or the quiz packets. Every time I have gone through an entire quiz question packet I get 100% they over prepare you for the quizzes."

"I think a small, simple study guide would help to become familiar with the material."

"The study guide helps a lot. Thanks. Also the in class questions from last year's midterm helped a lot too."

"I think something that isn't helpful while studying for the midterm is that the quiz question packets don't have answers. Therefore, we can't check to see if our answers are right or wrong."

"I enjoy the Snowboarder Model for looking at which planets are visible at certain times of the day."

"It is helpful to look back at past quizzes to get a good idea of what the questions on the test will look like."

"While studying for the midterm I have found it helpful to go over the questions in the quiz packets that have been provided."

"I believe that doing the quiz question packets will help a lot for the midterm. I did that for the first time with the last quiz and it was my best one yet."

Astronomy current events question: short orbital period exoplanet NGTS-10b

Astronomy 210L, spring semester 2020
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!)

Tom Frew and Peter Thorley, "18-hour Year Planet on Edge of Destruction" (February 20, 2020)
warwick.ac.uk/newsandevents/pressreleases/18-hour_year_planet

Exoplanet NGTS-10b, which has an orbital period of only 18 hours, was discovered as it __________ its star.
(A) collided with.
(B) escaped from.
(C) formed around.
(D) passed in front of.
(E) magnetically interfered with.

Correct answer: (B)

Student responses
Sections 30679, 30680
(A) : 3 students
(B) : 1 student
(C) : 0 students
(D) : 23 students
(E) : 0 students

Astronomy current events question: Breakthrough Listen data related

Astronomy 210L, spring semester 2020
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!)

Robert Sanders, "Breakthrough Listen's Search for Intelligent Life (SETI) Releases Unprecedented Data Survey of Milky Way’s Galactic Center, Earth Transit Zone and Interstellar Comet 2I/Borisov" (February 14, 2020)
breakthroughinitiatives.org/news/28

The Breakthrough Listen Initiative publicly released for analysis __________ data from scanning our Milky Way galaxy. (A) cosmic string.
(B) dark matter.
(C) gravitational wave.
(D) archived photographic.
(E) radio emission.

Correct answer: (E)

Student responses
Sections 30679, 30680
(A) : 1 student
(B) : 0 students
(C) : 21 students
(D) : 1 student
(E) : 4 students

Astronomy current events question: modeling Mars' interior composition

Astronomy 210L, spring semester 2020
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!)

News release, "Journey to the Center of Mars" (February 10, 2020)
tohoku.ac.jp/en/press/journey_to_the_center_of_mars.html

Researchers used analysis of rocks and satellite images to generate a model for Mars':
(A) seismic activity.
(B) climate history.
(C) magnetic dynamo.
(D) volcanic output.
(E) interior composition.

Correct answer: (E)

Student responses
Sections 30679, 30680
(A) : 5 students
(B) : 1 student
(C) : 0 students
(D) : 0 students
(E) : 21 students

Physics quiz question: finding amount of unknown charge

Physics 205B Quiz 3, spring semester 2020
Cuesta College, San Luis Obispo, CA

A –4.5 nC point charge and an unknown positive point charge are held a distance of 3.0 cm apart. The magnitude of the electric force of the –4.5 nC charge on the unknown positive charge is 7.6×10^–5 N. The amount of the unknown positive charge is:
(A) 1.7×10^–9 C.
(B) 5.6×10^–8 C
(C) 1.7×10⁴ C.
(D) 4.5×10⁴ C.

Correct answer (highlight to unhide): (A)

The magnitude of the force on the unknown positive point charge is given by:

|F_{1 on 2}| = k·|q₁|·|q₂|/(r²),

where q₁ is the –4.5 nC point charge, and q₂ is the unknown positive charge. Then the absolute value of the unknown charge can then be solved for:

|q₂| = |F_{1 on 2}|·(r²)/(k·|q₁|),

|q₁| = |7.6×10^–5 N|·(0.030 m)²/((8.99×10⁹ N·m²/C²)·|–4.4×10^–9 C|),

|q₁| = 1.6907675195...×10^–9 C,

or to two significant figures, the amount of the unknown (positive) charge is (+)1.7×10^–9 C.

(Response (B) is |F_{1 on 2}|·r/(k·|q₁|); response (C) is |F_{1 on 2}|/|q₁| (which is the electric field of the unknown positive charge at the location of the –4.5 nC charge); and response (D) is k·|q₁|/r² (which is the electric field of the –4.5 nC charge at the location of the unknown positive charge).)

Sections 30882, 30883
Exam code: quiz03Cv1d
(A) : 28 students
(B) : 1 student
(C) : 4 students
(D) : 1 student

Success level: 82%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.18

Physics quiz archive: interference, electrostatics

Physics 205B Quiz 3, spring semester 2020
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz03Cv1d



Sections 30882, 30883 results

0- 6 :
7-12 :
13-18 :	**** [low = 15]
19-24 :	***************
25-30 :	*************** [mean = 24.2 +/- 4.2] [high = 30]

Online reading assignment: capacitors

Physics 205B, spring semester 2020
Cuesta College, San Luis Obispo, CA

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

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


Selected/edited responses are given below.

Describe what you understand from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically demonstrate your level of understanding.

"The concept of the capacitor charging: in the GIF animation, the charging seems to be due to a negative charge leaving one side and when the negative charge leaves, a positive charge is left over. The positive charge then attracts a negative charge in the opposite side of the capacitor."

"The SI unit of capacitance is a farad, or coulombs squared over joules. Also that the capacitance is fixed once the construction of the capacitor is complete, and the only way to change the capacitance is to change the build of the capacitor. The potential applied to the capacitor can be altered however by using different batteries."

"A capacitor constructed from two plates and a space in-between. I also understand the capacitor construction formula."

"That once a capacitor is constructed you cannot change the capacitance of it without changing its build (plate area or separation distance)."

"Capacitors are built by putting parallel metal plates together with a small distance in between. Charging a capacitor requires a battery and will cause electrons to move freely from the top plate to the bottom plate until the top plate demonstrates a positive charge and the bottom plate have a negative charge. However, as more and more electrons move towards the bottom panel, it requires more work and creates a larger EPE charge due to the voltage."

"Capacitors store electric charge. Capacitors have a capacitance, which reflects their ability to store electric charge. While their capacitance is determined by surface area and separation distance of parallel metal plates, changing the voltage applied to the capacitor also changes their charge but does not change the capacitance of the capacitor."

"Capacitors store up electric potential energy by creating a potential difference across 2 parallel metal plates. The more charge the capacitor holds, the more energy it takes to move it across to the opposing plate. Unlike batteries, a charged capacitor can release its energy in a short burst over a short period of time."

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.

"Understanding voltage and especially understanding how it relates to capacitance is difficult."

"I don't understand how a capacitor gets charged."

"I do not understand capacitor charge because I see charges staying or leaving."

"Electric potential energy storage explanation."

"The capacitor energy storage formulas were different depending on the scenario. I need to work problems out to understand the differences."

"I found most of this reading assignment confusing. I could definitely use some clarification on the math."

"Nothing at this time, just want more examples of applications in class."

Describe two quantities that a capacitor is designed to store/hold.

"A capacitor is designed to hold voltage and electric potential energy."

"The capacitor holds charges. Both positive and negative?"

"Charge and electric potential energy."

State the unit of capacitance, and give its definition in terms of other SI units.

"farad, F, which is C (coulombs) squared divided by joules."

"Coulombs/volts = farads; where coulomb is electric charge, while volt is electric potential."

For a parallel-plate capacitor, ___________ the plate area and __________ the plate separation would increase its capacitance.

decreasing; decreasing.	[0]
decreasing; increasing.	** [2]
increasing; decreasing.	************************ [24]
increasing; increasing.	*** [3]
(Unsure/guessing/lost/help!)	*** [3]

For a parallel-plate capacitor, increasing the voltage (electric potential) difference applied to the capacitor would __________ the amount of charge stored in it.

decrease.	******* [7]
increase.	**************** [16]
have no effect on.	******* [7]
(Unsure/guessing/lost/help!)	**[2]

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

"I don't know. I would think increasing the voltage also increases the capacitance?"

"Because it only affects the actual amount of charge it has, not the storage ability, or size of the actual capacitor."

"The capacitor is based on the plate separation distance and cross-sectional area."

"The capacitor holds a specific amount and adding or decreasing the voltage does not change. This is due to the fact that once it is constructed, the capacitance is fixed."

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

"Do we get to use capacitors in any labs?"

"I am definitely struggling with this section, are we going to take a pretty deep dive on this?" (We will, but in lab.)

"Oh man, this electricity stuff is challenging."

"Capacitors shockingly weren't as difficult as I was anticipating."

"I noticed that farads are named after Michael Faraday. I hear his name mentioned a lot when discussing physics. Has he made a lot of contributions to the physics of electricity?" (Yes, but so did a lot of other physicists that have units named after them: Coulomb, Volta, Ohm, Ampere, Weber, Henry, and Tesla; along with others who don't have units named after them: Franklin, Maxwell, Ørsted, Lorentz, etc.)