Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz04Br7w
Sections 30882, 30883 results
| 0- 6 : | |
| 7-12 : | ******* [low = 9] |
| 13-18 : | ******** [mean = 17.1 +/- 5.4] |
| 19-24 : | ****** |
| 25-30 : | ** [high = 30] |
20170331
Physics quiz archive: capacitors, circuits
Physics 205B Quiz 4, spring semester 2017
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz04Br7w
Sections 30882, 30883 results
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz04Br7w
Sections 30882, 30883 results
Astronomy current events question: arcuate striations on Mars
Astronomy 210L, spring semester 2017
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!)
(A) ocean waves.
(B) dry ice snowfalls.
(C) magnetic pole fluctuations.
(D) dust storms.
(E) groundwater flooding.
Correct answer: (E)
Student responses
Sections 30679, 30680
(A) : 7 students
(B) : 1 student
(C) : 3 students
(D) : 6 students
(E) : 14 students
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!)
Thomas Deane, "Researchers Pinpoint Watery Past on Mars" (February 15, 2017)Comparison of "arcuate striations" in the Namib Desert on Earth with similar features on Mars observed by NASA's Mars Reconnaissance Orbiter indicate that both may be caused by repeated:
jpl.nasa.gov/spaceimages/details.php?id=PIA20521
(A) ocean waves.
(B) dry ice snowfalls.
(C) magnetic pole fluctuations.
(D) dust storms.
(E) groundwater flooding.
Correct answer: (E)
Student responses
Sections 30679, 30680
(A) : 7 students
(B) : 1 student
(C) : 3 students
(D) : 6 students
(E) : 14 students
Astronomy current events question: Dione's impact crater rays
Astronomy 210L, spring semester 2017
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!)
(A) chemical composition.
(B) sequence of events.
(C) radioactivity.
(D) water content.
(E) roughness.
Correct answer: (B)
Student responses
Sections 30679, 30680
(A) : 10 students
(B) : 12 students
(C) : 1 student
(D) : 2 students
(E) : 6 students
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!)
NASA/JPL-Caltech/Space Science Institute, "Rays of Creusa" (February 20, 2017)Rays of lighter ejected material from an impact crater on Saturn's moon, Dione observed by NASA's Cassini spacecraft can be used to determine the __________ of geological features on its surface.
jpl.nasa.gov/spaceimages/details.php?id=PIA20521
(A) chemical composition.
(B) sequence of events.
(C) radioactivity.
(D) water content.
(E) roughness.
Correct answer: (B)
Student responses
Sections 30679, 30680
(A) : 10 students
(B) : 12 students
(C) : 1 student
(D) : 2 students
(E) : 6 students
Astronomy current events question: Backyard Worlds crowdsource search
Astronomy 210L, spring semester 2017
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!)
(A) moving objects.
(B) infrared reflections.
(C) computer glitches.
(D) disrupted orbits.
(E) gravitational waves.
Correct answer: (A)
Student responses
Sections 30679, 30680
(A) : 9 students
(B) : 12 students
(C) : 3 students
(D) : 4 students
(E) : 3 students
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!)
Marc Kuchner, "Backyard Worlds: The Search for Planet 9" (February 15, 2017)Volunteers can assist with locating brown dwarfs or a possible "Planet Nine" by identifying __________ in NASA's Wide-field Infrared Survey Explorer (WISE) telescope images.
zooniverse.org/projects/marckuchner/backyard-worlds-planet-9/about/research
(A) moving objects.
(B) infrared reflections.
(C) computer glitches.
(D) disrupted orbits.
(E) gravitational waves.
Correct answer: (A)
Student responses
Sections 30679, 30680
(A) : 9 students
(B) : 12 students
(C) : 3 students
(D) : 4 students
(E) : 3 students
Online reading assignment: advanced electricity (review)
Physics 205B, spring semester 2017
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 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.
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.
What are the resistances of these (ideal) devices?
(Only correct responses shown.)
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.)
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.)
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
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 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.
"Kirchhoff's junction rule states that the sum of all the currents flowing into a system must be equivalent of the the current flowing out, Kirchhoff's loop rule states that there are rises and drops in potential but the net result in a complete loop stays the same. When an ammeter is used to break a circuit it essentially acts as a wire with zero resistance, in contrast a voltemeter has almost infinite resistance and will likely block any current if used to break a circuit."
"Kirchhoff's rules--for the junction rule the sum of all currents flowing into a junction must equal the sum of all the currents flowing out of the same junction. For the loop rule, if there is a complete loop in a circuit, where we end up at the same spot as we did when we started, all of the electric potential rises added together must equal all the electric potential drops added together."
"A change in electric potential represents the potential energy used by a charge. For each charge that uses a certain amount of electric potential, the amount of electric potential energy used is equal to charge times electric potential."
"Resistance increases in series circuits and decreases in parallel. Voltmeters measure potential and have high resistance, Ammeters measure current and have negligible resistance."
"I now understand how a voltmeter takes its reading of the change in voltage across a circuit by connecting in parallel to the system. Finding the current of the circuit and multiplying by each of the resistors between the connections of the voltmeter show the appropriate reading."
"As resistance goes down in a shorted battery circuit, there is more danger associated. For example, the gum wrapper being set on fire as it completed the circuit. Had the gum wrapper had a higher R value, there would be less risk of fire."
"Nothing, honestly."
Describe what you found confusing from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically identify the concept(s) that you do not understand.
"Not much, just need to do a few more circuit-solving problems."
"When you have to redraw the circuits because of parallel or not parallel. I just need to practice redrawing them."
"I think I need to see more examples of how to use the equations when using either an ammeter or a voltmeter."
"The different types of switches than can either be open or closed and the effect that has on resistance."
"The stuff that we covered on Monday in class with the voltmeter and ammeter stuff. I feel like there isn't enough understanding of the concept to go off of when we did the worksheet. So the worksheet was more so guessing my way through it than really understanding things. I left class with a bunch of question marks in my head."
"Using given equations to make substitutions for power dissipation."
"The power equations. I do not know how power can be expressed three different ways."
"A lot of stuff, as usual."
What are the resistances of these (ideal) devices?
(Only correct responses shown.)
Ideal light bulb: some finite value between 0 and ∞ [67%]
Burnt-out light bulb: ∞ [48%]
Ideal wire: 0 [52%]
Ideal (non-dead) battery: 0 [38%]
Real (non-dead) battery: some finite value between 0 and ∞ [76%]
Ideal switch, when open: ∞ [24%]
Ideal switch, when closed: 0 [33%]
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) [14%]
Larger potential potential difference: light bulb R [52%]
More power used: light bulb R [57%]
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 [57%]
Larger potential potential difference: (there is a tie) [38%]
More power used: light bulb r [38%]
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Could we go over power dissipation examples?"
"Doing Monday's lab really helped me distinguish the difference between an ammeter and a voltmeter and what each one measures."
"What makes the resistivity of materials strongly dependent on temperature?" (Since current is the flow of electrons, there are two things that either help or do not help these electrons move. The speed of these electrons depends on the temperature--cold temperatures mean that they can move slowly, and hot temperatures mean that they can move quickly, so raising the temperature tends to increase the speed of electrons and decrease the resistivity of the material. However, electrons need to pass through all the atoms in the material, and the vibrational motion of these stationary atoms also depends on the temperature--cold temperatures mean that they randomly vibrate very little, and hot temperatures mean that they randomly vibrate a lot, so raising the temperature tends to increase the random vibrations of the atoms, which can "block" to motion of electrons, and increase the resistivity of the material. These are two competing effects, and for different materials one effect will typically dominate over the other, and even this might change at different temperature ranges for the same material.)
"I don't understand how adding plugs will become dangerous when the ideal wires have low resistance." (If you start to add more resistors in parallel, the equivalent resistance will begin to decrease. E.g., five 100 Ω resistors in parallel have an equivalent resistance of 20 Ω, ten Ω resistors in parallel have an equivalent resistance of 10 Ω. Since all the outlets in a single household circuit are wired in parallel, plugging in more appliances (with a given resistance) means more are connected in parallel with each other; and then the equivalent resistance goes down, and the amount of current that will flow through the wire supplying that part of the house will increase. Power dissipated in the wire is I2·R, so even if the resistance of the wire is small, the current-squared will be very high, and the wire can get dangerously hot enough to melt its insulation wrapping, and start a fire behind the walls!)
"Why can we disregard the positive versus negative flow when dealing with an ideal battery? "For an emf source (such as an ideal battery) with a potential difference of ε, we do not pay attention to the direction of current flowing through the battery, but instead watch how we move through the battery with respect to the positive (+) and negative (–) terminals, which respectively represent the higher and lower electrical potential ends of the battery." (If this sounds non-physical, it kind of is--this is done when applying the loop rule (looking for potential drops and rises), so "walking around" a loop may or may not correspond to the actual flow direction of current. When applying the loop rule, if you travel into the (–) terminal and out of the (+) terminal of a battery, then you increase in potential (this is the conventional way a battery would be placed in a circuit); but if you happen to travel into the (+) terminal and out of the (–) terminal of a battery (which means that it is put in "backwards"), then you decrease in potential.)
"Brooo, it's April already." (We're still in March. #toosoon)
20170329
Astronomy quiz question: comparing star distances from apparent magnitudes, absolute magnitudes
Astronomy 210 Quiz 5, spring semester 2017
Cuesta College, San Luis Obispo, CA
The apparent magnitudes and absolute magnitudes of three stars are listed below.
Which star is nearest to Earth?
(A) G 29-38.
(B) Gliese 412B.
(C) YZ Ceti.
(D) (There is a tie.)
Correct answer (highlight to unhide): (C)
G 29-38 appears to have a brightness of +13 as seen from its actual location from Earth, but when placed at the "fair" distance of 10 parsecs away, it becomes brighter (+12). This means that G 29-38 was brought closer to Earth when moved to 10 parsecs, and thus is located farther than 10 parsecs away from Earth.
Both Gliese 412B and YZ Ceti get dimmer when moved from their actual locations from Earth to be placed at the "fair" distance of 10 parsecs away. This means that both Gliese 412B and YZ Ceti were pushed away from Earth when moved to 10 parsecs, and thus are both located closer than 10 parsecs away from Earth.
Since YZ Ceti gets dimmer by +2 (from +12 to +14) when pushed away from Earth, and Gliese 412B only gets dimmer by +1 (from +15 to +16) when pushed away from Earth, YZ Ceti was pushed back a greater distance away from its original location to 10 parsecs away, while Gliese 412B was only pushed back a small distance from its original location to 10 parsecs away. Thus YZ Ceti is closer to Earth than Gliese 412B (and G 29-38 is farthest away of all these three stars).
Section 30674
Exam code: quiz05ne0W
(A) : 5 students
(B) : 1 student
(C) : 14 students
(D) : 2 students
Success level: 65% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.80
Section 30676
Exam code: quiz05s4Ha
(A) : 7 students
(B) : 4 students
(C) : 25 students
(D) : 5 students
Success level: 63% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.46
Cuesta College, San Luis Obispo, CA
The apparent magnitudes and absolute magnitudes of three stars are listed below.
| m apparent magnitude |
M absolute magnitude |
|
| G 29-38 | +13 | +12 |
| Gliese 412B | +15 | +16 |
| YZ Ceti | +12 | +14 |
Which star is nearest to Earth?
(A) G 29-38.
(B) Gliese 412B.
(C) YZ Ceti.
(D) (There is a tie.)
Correct answer (highlight to unhide): (C)
G 29-38 appears to have a brightness of +13 as seen from its actual location from Earth, but when placed at the "fair" distance of 10 parsecs away, it becomes brighter (+12). This means that G 29-38 was brought closer to Earth when moved to 10 parsecs, and thus is located farther than 10 parsecs away from Earth.
Both Gliese 412B and YZ Ceti get dimmer when moved from their actual locations from Earth to be placed at the "fair" distance of 10 parsecs away. This means that both Gliese 412B and YZ Ceti were pushed away from Earth when moved to 10 parsecs, and thus are both located closer than 10 parsecs away from Earth.
Since YZ Ceti gets dimmer by +2 (from +12 to +14) when pushed away from Earth, and Gliese 412B only gets dimmer by +1 (from +15 to +16) when pushed away from Earth, YZ Ceti was pushed back a greater distance away from its original location to 10 parsecs away, while Gliese 412B was only pushed back a small distance from its original location to 10 parsecs away. Thus YZ Ceti is closer to Earth than Gliese 412B (and G 29-38 is farthest away of all these three stars).
Section 30674
Exam code: quiz05ne0W
(A) : 5 students
(B) : 1 student
(C) : 14 students
(D) : 2 students
Success level: 65% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.80
Section 30676
Exam code: quiz05s4Ha
(A) : 7 students
(B) : 4 students
(C) : 25 students
(D) : 5 students
Success level: 63% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.46
Astronomy quiz question: coolest star?
Astronomy 210 Quiz 5, spring semester 2017
Cuesta College, San Luis Obispo, CA
Which star is the coolest?
(A) A0 supergiant.
(B) M5 giant.
(C) F5 main-sequence star.
(D) B5 white dwarf.
(E) (There is a tie.)
Correct answer (highlight to unhide): (D)
An H-R diagram is provided with this quiz.
These stars are plotted on an H-R diagram below. The M5 giant is the coolest, followed by the F5 main-sequence star, the A0 supergiant, and the B5 white dwarf is the hottest. Instead of using the H-R diagram, the OBAFGKM mnemonic can be used to determine the temperatures of these stars from their spectral type.
Section 30676
Exam code: quiz05s4Ha
(A) : 3 students
(B) : 29 students
(C) : 0 students
(D) : 7 students
(E) : 2 students
Success level: 72% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.74
Cuesta College, San Luis Obispo, CA
Which star is the coolest?
(A) A0 supergiant.
(B) M5 giant.
(C) F5 main-sequence star.
(D) B5 white dwarf.
(E) (There is a tie.)
Correct answer (highlight to unhide): (D)
An H-R diagram is provided with this quiz.
These stars are plotted on an H-R diagram below. The M5 giant is the coolest, followed by the F5 main-sequence star, the A0 supergiant, and the B5 white dwarf is the hottest. Instead of using the H-R diagram, the OBAFGKM mnemonic can be used to determine the temperatures of these stars from their spectral type.
Section 30676
Exam code: quiz05s4Ha
(A) : 3 students
(B) : 29 students
(C) : 0 students
(D) : 7 students
(E) : 2 students
Success level: 72% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.74
Astronomy quiz question: hottest star?
Astronomy 210 Quiz 5, spring semester 2017
Cuesta College, San Luis Obispo, CA
Which star is the hottest?
(A) A0 supergiant.
(B) M5 giant.
(C) F5 main-sequence star.
(D) B5 white dwarf.
(E) (There is a tie.)
Correct answer (highlight to unhide): (D)
An H-R diagram is provided with this quiz.
These stars are plotted on an H-R diagram below. The B5 white dwarf is the hottest, followed by the A0 supergiant, the F5 main-sequence star, and the M5 giant is the coolest. Instead of using the H-R diagram, the OBAFGKM mnemonic can be used to determine the temperatures of these stars from their spectral type.
Section 30674
Exam code: quiz05ne0W
(A) : 2 students
(B) : 0 students
(C) : 0 students
(D) : 20 students
(E) : 0 students
Success level: 91% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.40
Cuesta College, San Luis Obispo, CA
Which star is the hottest?
(A) A0 supergiant.
(B) M5 giant.
(C) F5 main-sequence star.
(D) B5 white dwarf.
(E) (There is a tie.)
Correct answer (highlight to unhide): (D)
An H-R diagram is provided with this quiz.
These stars are plotted on an H-R diagram below. The B5 white dwarf is the hottest, followed by the A0 supergiant, the F5 main-sequence star, and the M5 giant is the coolest. Instead of using the H-R diagram, the OBAFGKM mnemonic can be used to determine the temperatures of these stars from their spectral type.
Section 30674
Exam code: quiz05ne0W
(A) : 2 students
(B) : 0 students
(C) : 0 students
(D) : 20 students
(E) : 0 students
Success level: 91% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.40
Astronomy quiz question: G5 supergiant vs. B5 main-sequence star
Astronomy 210 Quiz 5, spring semester 2017
Cuesta College, San Luis Obispo, CA
A G5 supergiant has a ___________ than a B5 main-sequence star.
(A) hotter temperature.
(B) brighter luminosity.
(C) larger size.
(D) (Two of the above choices.)
(E) (All of the above choices.)
(F) (None of the above choices.)
Correct answer (highlight to unhide): (D)
An H-R diagram is provided with this quiz.
These stars are plotted on an H-R diagram below. While the G5 supergiant has a brighter luminosity and a larger size, it has a cooler temperature than the G0 giant.
Section 30674
Exam code: quiz05ne0W
(A) : 0 students
(B) : 2 students
(C) : 0 students
(D) : 18 students
(E) : 2 students
(F) : 0 students
Success level: 82% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.40
Section 30676
Exam code: quiz05s4Ha
(A) : 0 students
(B) : 7 students
(C) : 5 students
(D) : 27 students
(E) : 2 students
(F) : 0 students
Success level: 68% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.82
Cuesta College, San Luis Obispo, CA
A G5 supergiant has a ___________ than a B5 main-sequence star.
(A) hotter temperature.
(B) brighter luminosity.
(C) larger size.
(D) (Two of the above choices.)
(E) (All of the above choices.)
(F) (None of the above choices.)
Correct answer (highlight to unhide): (D)
An H-R diagram is provided with this quiz.
These stars are plotted on an H-R diagram below. While the G5 supergiant has a brighter luminosity and a larger size, it has a cooler temperature than the G0 giant.
Section 30674
Exam code: quiz05ne0W
(A) : 0 students
(B) : 2 students
(C) : 0 students
(D) : 18 students
(E) : 2 students
(F) : 0 students
Success level: 82% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.40
Section 30676
Exam code: quiz05s4Ha
(A) : 0 students
(B) : 7 students
(C) : 5 students
(D) : 27 students
(E) : 2 students
(F) : 0 students
Success level: 68% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.82
Astronomy quiz question: K5 giant vs. M5 red dwarf
Astronomy 210 Quiz 5, spring semester 2017
Cuesta College, San Luis Obispo, CA
A K5 giant can have the same __________ as an M5 red dwarf.
(A) luminosity.
(B) size.
(C) temperature.
(D) (Two of the above choices.)
(E) (All of the above choices.)
(F) (None of the above choices.)
Correct answer (highlight to unhide): (F)
An H-R diagram is provided with this quiz.
These stars are plotted on an H-R diagram below. The K5 giant has a brighter luminosity, higher temperature, and a larger size than the M5 red dwarf.
Section 30674
Exam code: quiz05ne0W
(A) : 2 students
(B) : 1 student
(C) : 4 students
(D) : 0 students
(E) : 0 students
(F) : 15 students
Success level: 69% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.60
Section 30676
Exam code: quiz05s4Ha
(A) : 4 students
(B) : 2 students
(C) : 12 students
(D) : 3 students
(E) : 0 students
(F) : 20 students
Success level: 52% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.92
Cuesta College, San Luis Obispo, CA
A K5 giant can have the same __________ as an M5 red dwarf.
(A) luminosity.
(B) size.
(C) temperature.
(D) (Two of the above choices.)
(E) (All of the above choices.)
(F) (None of the above choices.)
Correct answer (highlight to unhide): (F)
An H-R diagram is provided with this quiz.
These stars are plotted on an H-R diagram below. The K5 giant has a brighter luminosity, higher temperature, and a larger size than the M5 red dwarf.
Section 30674
Exam code: quiz05ne0W
(A) : 2 students
(B) : 1 student
(C) : 4 students
(D) : 0 students
(E) : 0 students
(F) : 15 students
Success level: 69% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.60
Section 30676
Exam code: quiz05s4Ha
(A) : 4 students
(B) : 2 students
(C) : 12 students
(D) : 3 students
(E) : 0 students
(F) : 20 students
Success level: 52% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.92
Astronomy quiz archive: sun/spectra/star properties
Astronomy 210 Quiz 5, spring semester 2017
Cuesta College, San Luis Obispo, CA
Section 30674, version 1
Exam code: quiz05ne0W
Section 30674
Section 30676, version 1
Exam code: quiz05s4Ha
Section 30676
Cuesta College, San Luis Obispo, CA
Section 30674, version 1
Exam code: quiz05ne0W
Section 30674
| 0- 8.0 : | * [low = 8.0] |
| 8.5-16.0 : | * |
| 16.5-24.0 : | *** |
| 24.5-32.0 : | ************ [mean = 26.8 +/- 7.5] |
| 32.5-40.0 : | ***** [high = 40.0] |
Section 30676, version 1
Exam code: quiz05s4Ha
Section 30676
| 0- 8.0 : | * [low = 1.5] |
| 8.5-16.0 : | **** |
| 16.5-24.0 : | ********** |
| 24.5-32.0 : | ************** [mean = 26.5 +/- 7.9] |
| 32.5-40.0 : | ************ [high = 40.0] |
Online reading assignment: fusion, nebulae, star cluster ages (SLO campus)
Astronomy 210, spring semester 2017
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 fusion, nebulae, and star cluster ages.
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.
Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
Rank the luminosities of these main-sequence stars (1 = brightest, 3 = dimmest). (There are no ties.)
(Only correct responses shown.)
Rank the fusion rates of these main-sequence stars (1 = fastest, 3 = slowest). (There are no ties.)
(Only correct responses shown.)
Fusion requires high temperatures in order for nuclei to move quickly enough to:
Briefly explain why "cold fusion" (producing energy from hydrogen fusion at room temperature) would be implausible.
Match the three different types of nebulae with their colors.
(Only correct responses shown.)
Match the three different types of nebulae with their composition.
(Only correct responses shown.)
Rank the lifetimes of these main-sequence stars (1 = shortest, 3 = longest). (There are no ties.)
(Only correct responses shown.)
If there was an open invitation to a house party (no specific time given), when would you show up?
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
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 fusion, nebulae, and star cluster ages.
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 2.2 lbs of matter completely converted to energy produces enough energy to power Philadelphia for a year. Damn boi."
"Something I found interesting and super-fascinating as always is how absolutely stunning stars are. They are so beautiful--I don't think the night sky gets enough credit!"
"Hydrostatic equilibrium--I just had never thought about the layers of the sun, let alone layers of any object really applying pressure to the layer directly beneath it."
"I thought the comparison of our sun to cheerleaders was interesting and helpful because the example made it much easier to understand."
"The way nebulae have different colors and compositions I found really interesting. It makes me realize how little most of the population knows about the universe beyond earth."
"I really liked the explanation of the house party; it helped that section make a little better sense. And the pictures were funny! I also found the different colors of nebulae really cool!"
"The house party model, because it makes complete sense on how the stars age and behave."
"I found the representation of the house partiers for the star cluster age actually really helpful!"
"I found your house party model to be interesting, it was very amusing. I also was very intrigued by the process of the star formation, the supernova shock wave is very wind-blowing and amazing how it sort of jump-starts the formation of the star."
"I expected everything to be backwards like week, but I was pleasetly surprised everything made logical sense."
"I'm lost."
Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"Still confusing to me is how blue and white both are hotter than red. It just seems so backwards!"
"Comparing luminosities and fusion lifetimes."
"The concept of fusion and exactly what it has to 'overcome.'"
"I didn't really understand how the proton-proton chain worked."
"I have absolutely no idea what is going on with the interstellar medium."
"The difference between reflection and emission nebulae is confusing because I'm still unclear about how the different colors come about."
"I was a little confused on how we tell a star cluster's age."
"I am still really confused about this house party scenario! I can't wait to get it!"
"Everything seemed pretty straightforward."
"Not sure yet."
"So very lost."
Rank the luminosities of these main-sequence stars (1 = brightest, 3 = dimmest). (There are no ties.)
(Only correct responses shown.)
Massive: brightest luminosity [87%]
Medium-mass (sunlike): medium luminosity [92%]
Low mass (red dwarf): dimmest luminosity [89%]
Rank the fusion rates of these main-sequence stars (1 = fastest, 3 = slowest). (There are no ties.)
(Only correct responses shown.)
Massive: fastest fusion rate [87%]
Medium-mass (sunlike): medium fusion rate [95%]
Low mass (red dwarf): slowest fusion rate [87%]
Fusion requires high temperatures in order for nuclei to move quickly enough to:
break heavy elements apart. ***** [5] create convection currents. *** [3] overcome gravity. ****** [6] overcome repulsion. *************** [15] (Unsure/guessing/lost/help!) ********* [9]
Briefly explain why "cold fusion" (producing energy from hydrogen fusion at room temperature) would be implausible.
"Cold fusion wouldn't work because nuclear fusion only occurs when the nuclei of two atoms get very close to each other. These violent collisions only occur when hydrogen gas is very hot, like at the core of stars."
"Fusion requires sufficiently higher temperatures and pressures to take place. Room temperature would not do anything."
"At cooler temperatures, particles move more slowly. Slow protons will repel each other because of their positive charges."
"They have to be hot to move fast or aggressive enough to overcome their mutual repulsion."
"Hydrogen has a positive charge so it repels each other and cold temperatures won't allow to move fast enough to collide with each other."
"The pressure that occurs in stars can't be replicated (yet)."
"It is only a hypothesis, it naturally happens within stars at millions of degrees so cold fusion isn't plausible at cold or room temperature."
Match the three different types of nebulae with their colors.
(Only correct responses shown.)
Emission: pink [79%]
Reflection: blue [79%]
Dark: brown/black [97%]
Match the three different types of nebulae with their composition.
(Only correct responses shown.)
Emission: hydrogen [95%]
Reflection: small dust particles [89%]
Dark: large dust particles [89%]
Rank the lifetimes of these main-sequence stars (1 = shortest, 3 = longest). (There are no ties.)
(Only correct responses shown.)
Massive: shortest main-sequence lifetime [71%]
Medium-mass (sunlike): medium main-sequence lifetime [89%]
Low mass (red dwarf): longest main-sequence lifetime [68%]
If there was an open invitation to a house party (no specific time given), when would you show up?
Early, or on time. ****** [6] When the most people should be there. ******************************* [31] After most everyone has left. * [1]
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Will you throw a house party? (ಠ_ಠ)
"The house party question threw me off because it made me pick between always wanting to be early/on time and not wanting to be bored because everyone else came later. In the end I listened to my anxiety ¯\_(ツ)_/¯"
"I'm now referring to my party guests as low-mass stars, medium-mass stars, and massive stars."
"What time would you show up at a house party?" (Mrs. P-dog and I are always just a little fashionably late. But you would never know when we leave, if we do an Irish goodbye.)
"Will we get more practice with the H-R diagram and how to find out how close/far the stars are from the sun?" (Let's see how well you do on Quiz 5; and we'll have a review session for these topics before the next midterm.)
"Will there be a study guide for second midterm?" (Yes. But survive Quiz 6 first.)
"No comment." (You just did.)
"I found brown dwarfs a little confusing. Are they still gaseous and just don't have any nuclear fusion happening or are they solid mass?" (They're gaseous, just not large enough to have enough gravity to squeeze their cores to fuse hydrogen. So they didn't make the minimum mass/gravity/core squeezing requirement to be a star (generating energy from hydrogen fusion).)
"How is it possible to measure a star's energy output?" (From measuring the star's luminosity--the amount of energy produced by fusion in its core each second must be equal to the amount of energy it gives off in the form of light at its surface.)
"I wish we could do these online reading assignments up until the day of class." (But I need the day of class to read everyone's responses and decide what specific topics to cover in class.)
"Answering this question isn't part of the grade on the online assignment, is it? (It's optional compared to the other questions, I mean.)" (Yes, this last section is optional. However, if you leave a lot of the sections above blank, then you can make up for that by leaving something substantial here.)
"What are your plans for spring break, P-dog?" (Going camping with Mrs. P-dog and Slumberjack, the Sleeping Forester. #optoutside)
20170328
Online reading assignment: fusion, nebulae, star cluster ages (NC campus)
Astronomy 210, spring semester 2017
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 fusion, nebulae, and star cluster ages.
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.
Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
Rank the luminosities of these main-sequence stars (1 = brightest, 3 = dimmest). (There are no ties.)
(Only correct responses shown.)
Rank the fusion rates of these main-sequence stars (1 = fastest, 3 = slowest). (There are no ties.)
(Only correct responses shown.)
Fusion requires high temperatures in order for nuclei to move quickly enough to:
Briefly explain why "cold fusion" (producing energy from hydrogen fusion at room temperature) would be implausible.
Match the three different types of nebulae with their colors.
(Only correct responses shown.)
Match the three different types of nebulae with their composition.
(Only correct responses shown.)
Rank the lifetimes of these main-sequence stars (1 = shortest, 3 = longest). (There are no ties.)
(Only correct responses shown.)
If there was an open invitation to a house party (no specific time given), when would you show up?
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
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 fusion, nebulae, and star cluster ages.
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 learning about the fusion process to be very interesting, as it helps me get a better understanding of how stars develop and live their life."
"I understand why the sky appears to be blue. I have vindication for child me arguing about the color of the sky (literally)."
"I found the different colors connected to the different nebulaes very interesting, as well as their amounts of particles/lack of."
"It was interesting to look at the different nebula and see the colors that the human eye perceives."
"The colors and shapes of the nebulae, they were really beautiful and interesting."
"I thought the house party model was pretty cool. Totally relatable and made it easy to remember the differences between the star masses and the length of time they 'live.'"
"I found it interesting that a white dwarf is denser then a giant star. I though the bigger the denser, but I guess not when it comes to stars."
"It's crazy that the mass of white dwarfs is so dense that one teaspoon of it would weigh 15 tons on Earth."
"Cold fusion was an interesting topic because of how it isn't possible."
"How you used the cheerleader model to explain how fusion works in a star."
"Interstellar reddening giving the color to things such as the sunset. I didn't think the atmosphere provided a filter to change the glow of the sun and stars."
"That star cluster stars are all born at the same time but age differently because its interesting that they are in a sense like us with people we are the same age as and but we all age differently."
"That average stars spend 90% of its life on the main sequence."
Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"I find fusion to be very confusing, as there are many terms in the description of this process that I have forgotten or have become 'fuzzy' on."
"Nebulae, in general."
"It was hard to tell when the stars were coming or going on the main sequence line. Because most were on the right side where they could either be coming or going."
"I'm pretty confident that I understand the material covered in these sections. I'm sure I'll be able to concoct a question in class though. Usually once I hear other students' ideas it sparks questions!"
"The proton-proton chain, was confusing to me just understanding the terminology."
"The house party model--I was struggling to understand the turn-off points and main sequence line."
"How you can tell which star has the best fusion rate."
"Star clusters and how they explain stellar evolution."
"All of the star cluster age information--the H-R diagram didn't resonate with me and the turn-off point didn't make sense."
Rank the luminosities of these main-sequence stars (1 = brightest, 3 = dimmest). (There are no ties.)
(Only correct responses shown.)
Massive: brightest luminosity [95%]
Medium-mass (sunlike): medium luminosity [95%]
Low mass (red dwarf): dimmest luminosity [100%]
Rank the fusion rates of these main-sequence stars (1 = fastest, 3 = slowest). (There are no ties.)
(Only correct responses shown.)
Massive: fastest fusion rate [75%]
Medium-mass (sunlike): medium fusion rate [100%]
Low mass (red dwarf): slowest fusion rate [75%]
Fusion requires high temperatures in order for nuclei to move quickly enough to:
break heavy elements apart. ** [2] create convection currents. * [1] overcome gravity. * [1] overcome repulsion. ************** [14] (Unsure/guessing/lost/help!) ** [2]
Briefly explain why "cold fusion" (producing energy from hydrogen fusion at room temperature) would be implausible.
"Would be implausible due to the fact that heat is needed for any sort of fusion."
"Because fusion requires high temperatures. So if there is low pressure and low temperature, then there fusion would be low or not at all."
"The atoms are not moving fast enough to get through repulsion, so they would not collide or fuse."
"Cold fusion' is implausible, because in order for fusion to occur, the hydrogen atoms have to be squeezed a lot and moving very quickly. If the temperature isn't high enough then the hydrogen atoms won't move fast enough to fuse together."
"A hydrogen nucleus is just a proton so both would be positively charged and like charges repel."
Match the three different types of nebulae with their colors.
(Only correct responses shown.)
Emission: pink [90%]
Reflection: blue [90%]
Dark: brown/black [100%]
Match the three different types of nebulae with their composition.
(Only correct responses shown.)
Emission: hydrogen [95%]
Reflection: small dust particles [100%]
Dark: large dust particles [95%]
Rank the lifetimes of these main-sequence stars (1 = shortest, 3 = longest). (There are no ties.)
(Only correct responses shown.)
Massive: shortest main-sequence lifetime [70%]
Medium-mass (sunlike): medium main-sequence lifetime [90%]
Low mass (red dwarf): longest main-sequence lifetime [75%]
If there was an open invitation to a house party (no specific time given), when would you show up?
Early, or on time. ***** [5] When the most people should be there. ************** [14] After most everyone has left. * [1]
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Living on Earth might be expensive but at least you get a free trip around the sun every year."
"How long does it typically take for dust clusters to turn into stars whether kickstarted or regular pace?" (If not kickstarted by a nearby supernova, then it takes less than a million years for a molecular cloud to collapse into a massive star (because there's more gravity); or 10 million years or more for lower mass stars (with less gravity to gather up material.)
"Since there is a pattern for the main sequence stars (mass proportional to luminosity), what relationships (if any) apply for the 'other stars?'" (All the main-sequence stars are fusing hydrogen, so all their luminosities are related to their masses. However, all the "other stars" are dying or dead stars, having already used up all their available hydrogen, so their luminosities are either produced by stop-gap energy sources, or whatever energy is leftover after no more is produced--that's why all their luminosity values are all over the place compared to their masses.)
"Are you planning on throwing a house party, and are we invited?" (There is no actual house party. ಠ_ಠ)
"I show up early to a house party of a good friend."
"You know, seeing as I'm not super-hella social, I honestly probably wouldn't go to a house party. If I were to go to one, I would probably go between the 'on-time' and 'once people are already there,' but at the same time I would probably leave sooner rather than later..."
"Do we need to know the speed of the the massive, medium mass, and low mass star evolution tracks on an H-R diagram?" (Yes, that's part of the house party model.)
"I think it would be good if we could have more of a comprehensive or specific study guide for the next midterm. You said that it would be more technical because we are dealing with some harder topics, so a study guide could really help direct us to what we should specifically study."
"The reading explained that eventually the sun would increase in luminosity and destroy Earth; is there evidence of this happened to other planets?" (Yes, the red giant BD+48 740 contains lots of lithium, which is not produced in stars, and is easily broken down by star's high temperature, but is abundant in terrestrial planets--this is interpreted as evidence that BD+48 740 swallowed up at least one of its inner planets as it expanded into a red giant.)
"Can fission happen with lighter atoms? Why just heavy atoms like uranium--is it unstable and thus easier to break down? It's confusing because I can't find the answer without reading a hella-long webpage written for people who already understand it." (Uranium and other heavy atoms have lots of protons, which all repel each other, and are easier to break apart if they don't have just the right amount of neutrons to help them "stick" to each other. Since lighter atoms they have fewer protons and less repulsion, they're not as likely to fall apart unless they have a very unfavorable amount of neutrons to stick everything together.)
"How do you assign the seating charts? Is it completely random or do you keep certain people with certain people?" (I tend to keep people that are equally as smart as each other from being in the same group, in order to make each group a good "mixture" of students.)
I'm a little confused about brown dwarfs. Are they actually stars?" (They're just "failed" stars, because they don't have enough pressure in the cores to start hydrogen fusion. They're less massive than red dwarfs, which have just enough mass to create pressure in their cores to have hydrogen fusion.)
"I really appreciate the blog presentations. I find those much more understandable than reading out of the book."
20170327
Online reading assignment: advanced electricity
Physics 205B, spring semester 2017
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 reviewing presentations on circuit analysis and previewing presentations on advanced electricity concepts.
Selected/edited responses are given below.
Describe what you understand from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically demonstrate your level of understanding.
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.
What are the resistances of these (ideal) devices?
(Only correct responses shown.)
State the unit of electrical power, and give an equivalent definition in terms of other SI units.
(Only correct responses shown.)
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
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 reviewing presentations on circuit analysis and previewing presentations on advanced electricity concepts.
Selected/edited responses are given below.
Describe what you understand from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically demonstrate your level of understanding.
"When measuring the amount of electrical potential used by a light bulb (or any other circuit element), the digital multimeter must be connected to both before and after where the current flows through the light bulb. This means that the wiring in the circuit is not modified in order to connect the digital multimeter to measure electric potential (making it an voltmeter), as it 'feels' the amount of electric potential before and after the light bulb, and reports the difference (whether a drop or rise)."
"The more appliances that are plugged in an outlet, the resistance will decrease This can be very dangerous. Circuit breakers are to prevent current levels from reaching a dangerously high level--if the circuit breaker is triggered, this turns off the electricity so that the wires in the house do not become a danger to one's household."
"All household electrical outlets provide 120 volts of electric potential and operate independently of each other. The outlets are wired in parallel to each other to the same 120 volt electromotive source."
"An ideal ammeter has zero resistance because it measures the current within a circuit. Resistance in the ammeter is added to the circuit, which causes a reduction in current (since it is added in series). This would result in an artificially low measurement of current within a circuit."
"Right now this makes sense, currents are measured with anmeters and it tells you how much is running though the circuit. Voltmeters are used to measure the change in EPE of the item that you are using."
"A voltmeter measures the amount of volts running through a circuit. It should be hooked up to the first part of the circuit and the last part of the circuit so that it can read the change in potential when the voltage goes through the light bulb or resistor. There should be a really good resistor in there so that all the voltage is used up as it goes back to the start of the circuit. An ammeter measures current that passes through a light bulb. Since the current must pass through the digital multimeter the wiring of the circuit must be opened up so that the ammeter can read the current going through the circuit. There should be no resistance in the ammeter because you want to measure the original amount of current running through it."
"I learned that ammeter measures current and must be 'broken into' the circuit in order for the current to flow through it and a voltmeter measures the voltage and does not need to be 'broken in' since it measures a potential differences. The resistance for a voltmeter is infinite to avoid any current going into the voltmeter where as with the ammeter, the current is zero to allow the current to flow freely."
"In this homework assignment, it explains how multimeters must be used correctly to measure accurately because they are breaking a circuit when used as an ammeter. When used as a voltmeter, a multimeter must be connected to both before and after the current flow through a light bulb."
"I love all of your mnemonics! That is the best way for me to remember things so it makes less work for me to have t come up with little rhymes! "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.
"What I found confusing a from this reading assignment was the many different equations. I believe I understood that the different terms are able to be substituted to be able to relate to some of the other equations. When applying the equations was confusing."
"What I found a little confusing was the difference between a voltmeter and an ammeter. I'm still not entirely sure what the difference is except that an ideal voltmeter should have a high resistance and the ideal ammeter should have almost no resistance."
"I don't think I could figure out which equations to use."
"I don't understand how P can equal change in ∆V2/R or I2 times R."
"I'd like some more explanation on how multimeters measurements as ammeters and voltmeters differ. Also, how they relate to the equations."
"Nothing was confusing in the reading/lecture material. It was all pretty straightforward."
What are the resistances of these (ideal) devices?
(Only correct responses shown.)
Ideal ammeter: 0 [92%]
Ideal voltmeter: ∞ [80%]
State the unit of electrical power, and give an equivalent definition in terms of other SI units.
"The unit for power is watts (W), or joules (J) per second (s)."
"Not sure."
"Joules = newton·meters?"
"Volts?"
"Coulombs/second or joules/second?"
"Amps?"
(Only correct responses shown.)
Equivalent resistance Req of circuit: decreases [56%]
Current I flowing through emf source: increases [8%]
current. ******************** [20] voltage. ** [2] (Both of the above choices.) ** [2] (Neither of the above choices.) [0] (Unsure/guessing/lost/help!) * [1]
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Why does a circuit breaker trip when you have too many things plugged into outlets at your house?" (In a given room in your house, all the outlets are wired in parallel. Plugging in more appliances (each with a given resistance) means that they are all connected in parallel with each other; each additional appliance plugged in means that the equivalent resistance goes down, and thus the current going through the main wire to that part of the house goes up. A wire carrying a lot of current will tend to heat up, and if it is more current that it is rated for, then there is a fire risk, unless the circuit breaker trips.)
"It is scary to see the damage from a runaway current, that's why I'm not an electrician, haha! Circuit breakers and surge protectors must save a lot of buildings and lives!"
"When the resistance is low, the current is as fast as Usain Volt ; - )" (Well, not necessarily fast (all levels of currents travel at the same speed through a given wire); a better analogy would be that when resistance is low, current is as big as a football offensive line.)
"If power is the rate of electric potential energy (joules) per time, does that make it a second order derivative of electric potential?" (No, electric potential energy is not a derivative of electric potential ∆V, EPE (joules) is merely charge q (coulombs) times ∆V (joules/coulomb). So voltage is a ratio of energy per charge, rather than a "per time" derivative.)
"Why must a voltmeter have a resistance that is ideally infinity? I'm confused on this and what it means to have voltage." (If the voltmeter did not have an infinite resistance, then current would flow through it, and the voltmeter would then be measuring how much voltage is lost by the current flowing through itself, rather than measuring how much voltage is lost by what it is connected to (say, a disconnected battery, or a light bulb that has a given amount of current flowing through it.)
"Two parallel resistors double the resistance whereas two series resistors will halve the resistance." (#wut)
"Spring break!"
20170325
Physics midterm question: Boeing E-6A tail cable antenna reception
Physics 205B Midterm 1, spring semester 2017
Cuesta College, San Luis Obispo, CA
An airplane has a horizontal receiving antenna trailing behind it[*]. It can fly over a transmitting antenna that is aligned horizontally east-west. Discuss whether the airplane will receive more signal while flying over the transmitting antenna in the north-south direction (as shown here), or while flying over the transmitting antenna in the east-west direction, or if there is a tie. Explain your reasoning using the properties of light and polarization.
[*] fas.org/nuke/guide/usa/c3i/e-6.htm.
Solution and grading rubric:
Sections 30882, 30883
Exam code: midterm01AhC4
p: 16 students
r: 3 students
t: 5 students
v: 5 students
x: 1 student
y: 0 students
z: 0 student
A sample "p" response (from student 6969):
Cuesta College, San Luis Obispo, CA
An airplane has a horizontal receiving antenna trailing behind it[*]. It can fly over a transmitting antenna that is aligned horizontally east-west. Discuss whether the airplane will receive more signal while flying over the transmitting antenna in the north-south direction (as shown here), or while flying over the transmitting antenna in the east-west direction, or if there is a tie. Explain your reasoning using the properties of light and polarization. [*] fas.org/nuke/guide/usa/c3i/e-6.htm.
Solution and grading rubric:
- p:
Correct. Discusses/demonstrates that signal will be received by the airplane receiving antenna as it flies east-west over the transmitter, and no signal will be received as it flies north-south, because:- the east-west transmitter will emit a transverse wave straight upward that has the same east-west polarization as the antenna orientation (also along the north and south directions at ground level);
- a receiving antenna will best pick up a transverse radio wave when its orientation matches the polarization of the radio wave, and pick up no signal when its orientation is perpendicular to the polarization of the radio wave.
- r:
As (p), but argument indirectly, weakly, or only by definition supports the statement to be proven, or has minor inconsistencies or loopholes. May have a "T" at the end of the cable trailing the aircraft, such that its receiving orientation is parallel to its wings instead of parallel to its fuselage. - t:
Nearly correct, but argument has conceptual errors, or is incomplete. Typically only explanation for (1) is complete, but not (2). - v:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Some garbled attempt at applying the properties of light (radio waves) and polarization. - x:
Implementation/application of ideas, but credit given for effort rather than merit. No clear attempt at applying the properties of light (radio waves) and polarization. - y:
Irrelevant discussion/effectively blank. - z:
Blank.
Sections 30882, 30883
Exam code: midterm01AhC4
p: 16 students
r: 3 students
t: 5 students
v: 5 students
x: 1 student
y: 0 students
z: 0 student
A sample "p" response (from student 6969):
Physics midterm question: enlarged virtual image from converging lens
Physics 205B Midterm 1, spring semester 2017
Cuesta College, San Luis Obispo, CA
An object is placed in front of a converging lens, which results in a virtual image that is exactly 2× larger than the size of the object. Discuss why the object must be placed exactly halfway between the focal point and the lens for this to happen. Explain your reasoning by using ray tracings and/or thin lens equations, properties of lenses, images, and magnification.
Solution and grading rubric:
Sections 30882, 30883
Exam code: midterm01AhC4
p: 6 students
r: 4 students
t: 10 students
v: 7 students
x: 2 students
y: 0 students
z: 1 student
A sample "p" response (from student 6819):
Cuesta College, San Luis Obispo, CA
An object is placed in front of a converging lens, which results in a virtual image that is exactly 2× larger than the size of the object. Discuss why the object must be placed exactly halfway between the focal point and the lens for this to happen. Explain your reasoning by using ray tracings and/or thin lens equations, properties of lenses, images, and magnification.
Solution and grading rubric:
- p:
Correct. Discusses/demonstrates that a virtual image that twice the size of an object must be placed halfway between the focal point and a converging lens:- uses the linear magnification equation m = –di/do to find that di = –2·do (where m = +2, as virtual images are upright); and
- from the thin lens equation, substituting di = –2·do to eliminate di, and solving for do in terms of the focal length f results in do = f/2, thus the object must be placed halfway between the focal point and a converging lens; and/or
- assumes numerical values for the focal length, object distance and/or image distance to quantitatively result in a linear magnification factor of +2, with an object distance that is half of the numerical value of the focal length; and/or
- draws a carefully, properly scaled ray tracing diagram.
- r:
As (p), but argument indirectly, weakly, or only by definition supports the statement to be proven, or has minor inconsistencies or loopholes. May have negative sign errors in (1)-(2). - t:
Nearly correct, but argument has conceptual errors, or is incomplete. May have (1), but does not explicitly prove that do = f/2. - v:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Some garbled attempt at applying ray tracings and/or thin lens equations, properties of lenses, images, and linear magnification. - x:
Implementation/application of ideas, but credit given for effort rather than merit. No clear attempt at applying ray tracings and/or thin lens equations, properties of lenses, images, and linear magnification. - y:
Irrelevant discussion/effectively blank. - z:
Blank.
Sections 30882, 30883
Exam code: midterm01AhC4
p: 6 students
r: 4 students
t: 10 students
v: 7 students
x: 2 students
y: 0 students
z: 1 student
A sample "p" response (from student 6819):
Physics midterm question: comparing first and second maxima angles
Physics 205B Midterm 1, spring semester 2017
Cuesta College, San Luis Obispo, CA
A green laser (wavelength 550 nm) illuminates a compact disc (CD) disk with a track spacing of 1.6 µm[*], producing a set of maxima spots at certain angles. (Drawing is not to scale.) Discuss why the second maxima angle is not exactly twice the first maxima angle. Explain your reasoning using trigonometry, the properties of source phases, path lengths, and interference.
[*] en.wikipedia.org/wiki/File:Comparison_CD_DVD_HDDVD_BD.svg
Solution and grading rubric:
Sections 30882, 30883
Exam code: midterm01AhC4
p: 17 students
r: 2 students
t: 5 students
v: 1 student
x: 5 students
y: 0 students
z: 0 students
A sample "p" response (from student 2420):
Cuesta College, San Luis Obispo, CA
A green laser (wavelength 550 nm) illuminates a compact disc (CD) disk with a track spacing of 1.6 µm[*], producing a set of maxima spots at certain angles. (Drawing is not to scale.) Discuss why the second maxima angle is not exactly twice the first maxima angle. Explain your reasoning using trigonometry, the properties of source phases, path lengths, and interference. [*] en.wikipedia.org/wiki/File:Comparison_CD_DVD_HDDVD_BD.svg
![en.wikipedia.org/wiki/File:Comparison_CD_DVD_HDDVD_BD.svg](http://en.wikipedia.org/wiki/File:Comparison_CD_DVD_HDDVD_BD.svg"){kind=link}
Solution and grading rubric:
- p:
Correct. The second maxima angle is not exactly twice the first maxima angle, because given spacing d between tracks and the wavelength λ of the laser, from the maxima equation d·sinθ = m·λ the first maxima angle θ1 = sin–1(1·λ/d), and the second maxima angle θ2 = sin–1(2·λ/d), which is slightly more than twice θ1. - r:
As (p), but argument indirectly, weakly, or only by definition supports the statement to be proven, or has minor inconsistencies or loopholes. May have solved for second minima angle instead of second maxima angle. - t:
Nearly correct, but argument has conceptual errors, or is incomplete. At least has first maxima angle, or sets up work that would eventually result in finding and comparing first maxima angle with the second maxima angle. - v:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Some garbled attempt at applying trigonometry, properties of source phases, path lengths, and interference. - x:
Implementation/application of ideas, but credit given for effort rather than merit. No clear attempt at applying trigonometry, properties of source phases, path lengths, and interference. Focus on constructing triangles with CD-to-screen distance and spacing along screen distance to find angles, rather than appealing to properties of constructive interference along certain angles. - y:
Irrelevant discussion/effectively blank. - z:
Blank.
Sections 30882, 30883
Exam code: midterm01AhC4
p: 17 students
r: 2 students
t: 5 students
v: 1 student
x: 5 students
y: 0 students
z: 0 students
A sample "p" response (from student 2420):
Physics midterm question: non-zero total electric field between two charges
Physics 205B Midterm 1, spring semester 2017
Cuesta College, San Luis Obispo, CA
Two point charges are held at fixed locations at x = –2 cm and at x = +2 cm. The charge located at x = –2 cm is negatively charged, and the charge located at x = +2 cm is positively charged. Discuss why it is not possible for the electric field at the origin to be zero, for any possible numerical values (equal or unequal) for these two charges. Explain your reasoning using properties of electric forces, fields, and vector superposition.
Solution and grading rubric:
Sections 30882, 30883
Exam code: midterm01AhC4
p: 9 students
r: 12 students
t: 0 students
v: 9 students
x: 0 students
y: 0 students
z: 0 students
A sample "p" response (from student 1381):
Cuesta College, San Luis Obispo, CA
Two point charges are held at fixed locations at x = –2 cm and at x = +2 cm. The charge located at x = –2 cm is negatively charged, and the charge located at x = +2 cm is positively charged. Discuss why it is not possible for the electric field at the origin to be zero, for any possible numerical values (equal or unequal) for these two charges. Explain your reasoning using properties of electric forces, fields, and vector superposition. Solution and grading rubric:
- p:
Correct. The (total) electric field magnitude at x = 0 cannot be zero for any possible numerical values for the two source charges, because:- the electric field at x = 0 of the Q1 source charge points to the left (in towards this negative source charge), and the electric field at x = 0 of the Q2 source charge also points to the left (out away from this positive source charge), and;
- no matter what numerical values the two source charges have, since these two electric field vectors will add at x = 0 (because they point in the same direction, to the left), they cannot possibly cancel each other out.
- r:
Nearly correct, but includes minor math errors. May not explicitly discuss/demonstrate how the numerical values of the two source charges does not matter. - t:
Nearly correct, but approach has conceptual errors, and/or major/compounded math errors. - v:
Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner. Some garbled attempt at applying properties of electric forces, fields, and vector superposition. May discuss how the two charges attract each other, or has their electric fields pointing pointing in opposite directions at x = 0. - x:
Implementation of ideas, but credit given for effort rather than merit. No clear attempt at applying properties of electric forces, fields, and vector superposition. - y:
Irrelevant discussion/effectively blank. - z:
Blank.
Sections 30882, 30883
Exam code: midterm01AhC4
p: 9 students
r: 12 students
t: 0 students
v: 9 students
x: 0 students
y: 0 students
z: 0 students
A sample "p" response (from student 1381):
Physics midterm problem: extending telescope length
Physics 205B Midterm 1, spring semester 2017
Cuesta College, San Luis Obispo, CA
Two converging lenses, with focal lengths of +40.0 cm (for the objective lens) and +2.5 cm (for the eyepiece) are used to make a telescope. The length of the telescope (measured from lens-to-lens) is adjusted by sliding cardboard tubes in or out. Starting with the telescope used to look at an object very far away (essentially at infinity), determine how much the length must be extended in order to look at a closer object 10 m away. Show your work and explain your reasoning by using ray tracings and/or thin lens equations, properties of lenses, images, and magnification.
[*] Alan M. MacRobert, "Astronomy with a $5 Telescope," Sky & Telescope, vol. 79 no. 4 (April 1990), p. 384.
Solution and grading rubric:
Sections 30882, 30883
Exam code: midterm01AhC4
p: 5 students
r: 0 students
t: 7 students
v: 17 students
x: 1 student
y: 0 students
z: 0 students
A sample "p" response (from student 1412):
Cuesta College, San Luis Obispo, CA
Two converging lenses, with focal lengths of +40.0 cm (for the objective lens) and +2.5 cm (for the eyepiece) are used to make a telescope. The length of the telescope (measured from lens-to-lens) is adjusted by sliding cardboard tubes in or out. Starting with the telescope used to look at an object very far away (essentially at infinity), determine how much the length must be extended in order to look at a closer object 10 m away. Show your work and explain your reasoning by using ray tracings and/or thin lens equations, properties of lenses, images, and magnification.
[*] Alan M. MacRobert, "Astronomy with a $5 Telescope," Sky & Telescope, vol. 79 no. 4 (April 1990), p. 384.
Solution and grading rubric:
- p:
The eyepiece must be moved back by approximately 2 cm because:- the object at do1 = +∞ for the objective creates a real image at di1 = f1 = +40.0 cm, which becomes the object at a distance do2 = f2 = +2.5 cm for the eyepiece, thus the telescope length (lens-to-lens distance) is 40.0 cm + 2.5 cm = 42.5 cm;
- the object at do1 = +10 m for the objective creates a real image at a slightly farther distance of di1 = +41.7 cm, which becomes the object at the same distance do2 = f2 = +2.5 cm for the eyepiece, thus the telescope length (lens-to-lens distance) is now slightly longer: 41.7 cm + 2.5 cm = 44.2 cm;
- thus the slight increase (approximately 2 cm) in the objective image distance di1 requires the eyepiece to be moved back by the same amount in order for this image to be placed at its front focal point.
- r:
As (p), but argument indirectly, weakly, or only by definition supports the statement to be proven, or has minor inconsistencies or loopholes. - t:
Nearly correct, but approach has conceptual errors, and/or major/compounded math errors. At least understands that the telescope length is f1 + f2 when focused at ∞, and some attempt at finding the telescope length di1 + f2 when focused at a finite do1. - v:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Some garbled attempt at ray tracings and/or thin lens equations, the properties of lenses, images, and magnifications. May have used microscope magnification equation to find length between lenses. - x:
Implementation/application of ideas, but credit given for effort rather than merit. No clear attempt at applying ray tracings and/or thin lens equations, the properties of lenses, images, and magnifications. - y:
Irrelevant discussion/effectively blank. - z:
Blank.
Sections 30882, 30883
Exam code: midterm01AhC4
p: 5 students
r: 0 students
t: 7 students
v: 17 students
x: 1 student
y: 0 students
z: 0 students
A sample "p" response (from student 1412):
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