Found physics: joule thief

"101114-1200240"
Waifer X
flic.kr/p/8UVKH3

Joule thief (wki.pe/Joule_thief), built with Radio Shack parts and a mint tin, circuit diagram based on Make magazine's how-to tutorial (makezine.com/2007/11/02/make-a-joule-thief-weeken-1/).

Astronomy current events question: extra-galactic planet

Astronomy 210L, Fall Semester 2010
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!)

Alan MacRobert, "Planet from Another Galaxy," November 18, 2010
http://www.skyandtelescope.com/news/108739724.html

Astronomers were able to determine that the star HIP 13044 and its orbiting planet may have come from beyond the Milky Way galaxy by analyzing their:
(A) trajectory.
(B) metallicity.
(C) gravitational wobbles.
(D) orbital motion.
(E) absorption and emission spectra.

Correct answer: (A)

Student responses
Sections 70178, 70186, 70200
(A) : 5 students
(B) : 10 students
(C) : 8 students
(D) : 4 students
(E) : 3 students

Astronomy current events question: Rhea's thin atmosphere

Astronomy 210L, Fall Semester 2010
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!)

Jia-Rui C. Cook, "Thin Air--Cassini Finds Ethereal Atmosphere at Rhea," November 26, 2010
http://www.nasa.gov/mission_pages/cassini/whycassini/cassini20101126.html

The NASA Cassini spacecraft has detected a thin atmosphere around Saturn's moon Rhea, containing oxygen that may be released from:
(A) pockets containing pristine solar nebula gas.
(B) high energy particles bombarding its icy surface.
(C) subsurface organisms capable of photosynthesis.
(D) chemical processes that may eventually evolve into life.
(E) radioactive decay processes.

Correct answer: (B)

Student responses
Sections 70178, 70186, 70200
(A) : 4 students
(B) : 22 students
(C) : 7 students
(D) : 14 students
(E) : 8 students

Astronomy current events question: Jupiter's south equatorial belt

Astronomy 210L, Fall Semester 2010
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!)

Emily Lakdawalla, "Jupiter's Outbreak is Spreading," November 22, 2010
http://planetary.org/blog/article/00002784/

Amateur astronomers have been observing recent rapid changes in Jupiter's:
(A) two moons that may soon collide.
(B) polar ice caps.
(C) lightning storms.
(D) magnetic field.
(E) weather patterns.

Correct answer: (E)

Student responses
Sections 70178, 70186, 70200
(A) : 0 students
(B) : 1 student
(C) : 0 students
(D) : 5 students
(E) : 20 students

Astronomy midterm question: big bang not like an explosion?

Astronomy 210 Midterm 2, fall semester 2010
Cuesta College, San Luis Obispo, CA

[20 points.] Consider the following statement regarding the big bang:

"The big bang did not explode into space like a bomb exploding..."
--Sujoy Desai, Uniphase: A Solution to Albert Einstein's "The Unified Field Theory," iUniverse, Bloomington, IN, 2003, p. 10.

Discuss why this statement is correct, and how you know this. Explain using observations and evidence related to the Hubble law.

Solution and grading rubric:

• p = 20/20:
  Correct. Hubble's law is that the recession velocity of galaxies is proportional to distance, evidence is that there is a greater redshift of absorption lines for distant galaxies compared to nearby galaxies. This is in opposition to an explosion, where the velocity of particles is inversely proportional to the distance from the center of the explosion. (Or may use Hubble's law to argue that there is no unique center to the expansion of space, in opposition to an explosion, which does have a unique center.)
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Discusses how Hubble's law expansion is not like an explosion, but does not explicitly discuss absorption line redshift evidence for Hubble's law.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Describes how an explosion is not like the actual expansion of the universe, but Hubble's law discussion is problematic or incomplete.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Discussion based on evidence of the earlier stages in the history of the universe, with little or no substantive discussion of Hubble's law.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit.
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 70158
p: 8 students
r: 14 students
t: 7 students
v: 7 students
x: 9 students
y: 0 students
z: 1 student

A sample "p" response (from student 1122):
Another sample "p" response (from student 1021):
A sample "x" response (from student 4146):
A sample "x" response (from student 4130), tossing in a "bing bang [sic]" reference:
A sample "x" response (from student 7183), with a personal message:

Astronomy midterm question: massive star evolution

Astronomy 210 Midterm 2, fall semester 2010
Cuesta College, San Luis Obispo, CA

For the H-R diagram of a star cluster shown at right, decide whether the massive stars are in their protostar, main sequence, or supergiant phase, or if there are no massive stars in this star cluster, and how you know this. Explain your answer using the properties of stars and evolution times.

Solution and grading rubric:

• p = 20/20:
  Correct. Massive stars in this star cluster are supergiants (or there may be no massive stars left after exploding as type II supernovae). Understands that massive stars evolve faster than low-mass stars, such that by the time the low-mass stars to have nearly reached the lower right corner of the H-R diagram, the massive stars have already gone through their protostar and main sequence phases.
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. As (p), but with minor omissions, or while correctly identifying massive stars as being in their supergiant phase, focus of discussion is a (complete, correct) description of life stages of massive stars rather than recognizing the relative evolution rates and placement of medium- and low-mass stars on the star cluster H-R diagram.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Identifies upper right corner group of stars off the main sequence as supergiants, but does not plausibly rule out the possibility that they might be protostars instead (by discussing the relative positions of the medium- and low-mass stars).
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit. Conclusion without substantive argument.
  y = 2/20: Irrelevant discussion/effectively blank.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 70158
p: 21 students
r: 10 students
t: 9 students
v: 4 students
x: 2 students
y: 0 students
z: 0 students

A sample "p" response (from student 1234), discussing a "house party" model:
Another sample "p" response (from student 1122), also discussing a "house party" model:

Astronomy midterm question: no center for universe?

Astronomy 210 Midterm 2, Fall Semester 2010
Cuesta College, San Luis Obispo, CA

[20 points.] An astronomy question on an online discussion board (http://answers.yahoo.com/question/index?qid=20100905145749AAyQLJr) was asked and answered:

Bell: What is at the center of the universe?

Stimpy: The universe is not defined to have [a] center. Wherever you are in the universe you will always appear to be in the center.

Discuss why this answer is correct, and how you know this. Explain using observations and evidence related to the Hubble law.

Solution and grading rubric:

• p = 20/20:
  Correct. Hubble's law is that the recession velocity of galaxies is proportional to distance, evidence is that there is a greater redshift of absorption lines for distant galaxies compared to nearby galaxies. This corresponds to the expansion of space between galaxies, such that each galaxy seems to be center of expansion as observed from their position. May use analogies as not-like-an-explosion, raisin bread, enlargement of between-spaces, etc.
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Discusses how Hubble's law expansion will be observed identically for all viewpoints, but does not explicitly discuss absorption line redshift evidence for Hubble's law.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Describes how Hubble's law expansion will be observed identically for all viewpoints, but Hubble's law discussion is problematic or incomplete.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Discussion based on evidence of the earlier stages in the history of the universe, with little or no substantive discussion of Hubble's law.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit.
  y = 2/20: Irrelevant discussion/effectively blank.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 70160
p: 11 students
r: 10 students
t: 11 students
v: 5 students
x: 3 students
y: 1 student
z: 0 students

A sample "r" response (from student 2421):

Astronomy midterm question: monolithic collapse model

Astronomy 210 Midterm 2, Fall Semester 2010
Cuesta College, San Luis Obispo, CA

[20 points.] Discuss the evidence for the monolithic collapse model of the Milky Way (spherical gas cloud flattening into a disk). Support your answer using the orbit and metal content properties of halo stars versus disk stars.

Solution and grading rubric:

• p = 20/20:
  Correct. Discusses evidence supporting the flattening of the Milky Way's shape by explaining how metal content increases for younger generations of stars, and observations that disk stars are metal-rich compared to the metal-poor halo stars above and below the disk.
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. At least some discussion related to the monolothic collapse model.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit. Discussion unrelated to the monolithic collapse model.
  y = 2/20: Irrelevant discussion/effectively blank.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 70160
p: 17 students
r: 8 students
t: 4 students
v: 6 students
x: 3 students
y: 3 students
z: 0 students

A sample "p" response (from student 1991):

Astronomy midterm question: same size supergiant and giant stars

Astronomy 210 Midterm 2, fall semester 2010
Cuesta College, San Luis Obispo, CA

Discuss whether or not a supergiant and a giant star with the same size could have the same temperature, and why. Support your answer using the Stefan-Boltzmann law and/or an H-R diagram.

Solution and grading rubric:

• p:
  Correct. Uses either the H-R diagram and/or the Stefan-Boltzmann law to show that since all supergiants are more luminous than giants, then it is not possible for a supergiant and a giant to have the same size and same temperature (as that would result in the same luminosity).
  
• r:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
  
• t:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Attempts to use H-R diagram and/or Stefan-Boltzman law with stars of same size and same temperature, while realizing that supergiants and giants have different luminosities, but does not adequately resolve that these two arguments are inconsistent with each other (or resolves this with a plausible overlapping range of sizes/temperatures).
  
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. At least attempts to use H-R diagram and/or Stefan-Boltzman law.
  
• x:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y:
  Irrelevant discussion/effectively blank.
  
• z:
  Blank.
  

Grading distribution:
Section 70160
p: 21 students
r: 7 students
t: 6 students
v: 7 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 1204):

Another sample "p" response (from student 0002):

Physics midterm problem: total magnetic field of two current-carrying wires

Physics 205B Midterm 2, Fall Semester 2010
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 19.61

[20 points.] Two long straight wires carry different amounts of current in the plane of this page. Determine the direction and magnitude of the magnetic field at the location indicated. Show your work and explain your reasoning.

Solution and grading rubric:

• p = 20/20:
  Correct. Determines directions of the magnetic fields of each current separately at point P, where B_1 points into the page, and B_2 points out of the page. Finds the magnitudes of these magnetic fields, and since B_2 has a greater magnitude than B_1, the resulting total magnetic field at point P will point out of the page, with a (positive definite) magnitude that is the arithmetic difference of the two magnitudes.
  
• r = 16/20:
  Nearly correct, but includes minor math errors. Direction or magnitude of total magnetic field has minor error.
  
• t = 12/20:
  Nearly correct, but approach has conceptual errors, and/or major/compounded math errors. Both direction and magnitude of total magnetic field have minor errors.
  
• v = 8/20:
  Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner.
  
• x = 4/20:
  Implementation of ideas, but credit given for effort rather than merit.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 70856
p: 8 students
r: 1 student
t: 2 students
v: 0 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 8110):