Kudos: expanding my universe

"Expanding My Universe," by Student 2021
Astronomy 210
May 2015
Cuesta College, San Luis Obispo, CA

Kudos: different teaching style

"Different Teaching Style," by Student 1175
Astronomy 210
May 2015
Cuesta College, San Luis Obispo, CA

Physics quiz archive: radioactive decay, Feynman diagrams

Physics 205B Quiz 7, spring semester 2015
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz07d4wN


Sections 30882, 30883 results

0- 6 :	**** [low = 3]
7-12 :	******
13-18 :	*************
19-24 :	****** [mean = 18.4 +/- 7.8]
25-30 :	*********** [high = 30]

Astronomy midterm question: red supergiants versus red giants

Astronomy 210 Midterm 2, spring semester 2015
Cuesta College, San Luis Obispo, CA

An astronomy question on an online discussion board[*] was answered:

Yg: Red supergiants can be the same size as red giants.

Discuss why this answer is incorrect, and how you know this. Explain using Wien's law, the Stefan-Boltzmann law and/or an H-R diagram.

[*] answers.yahoo.com/question/index?qid=20150326215251AATYkHE.

Solution and grading rubric:

• p:
  Correct. Uses Wien's law, the Stefan-Boltzmann law and/or interprets H-R diagram to discuss how a red supergiant cannot be the size as a red giant by either arguing:
  1. that from Wien's law, a red supergiant must have the same temperature as a red giant, and from the H-R diagram a supergiant must be more luminous than a giant, such that from the Stefan-Boltzmann law, for two stars that have the same temperature, the more luminous supergiant must be larger than the less luminous giant, which makes it not possible for the supergiant to have the same size as the giant; or instead argues
  2. that from the Stefan-Boltzmann law, for two stars that have the same size, the more luminous supergiant must have a hotter surface temperature, which makes it not possible to have the same color as the less luminous giant.
• 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. At last discussion demonstrates understanding of Wien's law, H-R diagram and/or the Stefan-Boltzmann law.
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. At least attempts to use Wien's law, H-R diagram and/or the Stefan-Boltzmann law.
• x:
  Implementation/application of ideas, but credit given for effort rather than merit. Discussion not clearly based on Wien's law, H-R diagram and/or the Stefan-Boltzmann law.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.

Section 30674
Exam code: midterm02N4ra
p: 20 students
r: 1 student
t: 11 students
v: 4 students
x: 1 student
y: 1 student
z: 0 students

Section 30676
Exam code: midterm02s0Ju
p: 30 students
r: 5 students
t: 12 students
v: 2 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 2194):
A sample "t" response (from student 1175):

Astronomy midterm question: same or different distance stars?

Astronomy 210 Midterm 2, spring semester 2015
Cuesta College, San Luis Obispo, CA

An astronomy question on an online discussion board[*] was answered:

SM: If Star A has a dimmer apparent magnitude and a brighter absolute magnitude, and Star B has a brighter apparent magnitude and a dimmer absolute magnitude, they could not be the same distance from us.

Discuss why this reasoning is correct, and how you know this. Explain using the relationships between apparent magnitude, absolute magnitude, and distance.

[*] answers.yahoo.com/question/index?qid=20150326221032AADoWdf .

Solution and grading rubric:

• p:
  Correct. Understands difference between apparent magnitude m (brightness as seen from Earth, when placed at their actual distance from Earth) and absolute magnitude M (brightness as seen from Earth, when placed 10 parsecs away), and discusses how star A and star B cannot be located the same distance away from Earth by either arguing:
  1. how star A (which seems dim (m) but is actually bright (M) when placed at 10 parsecs away) must be located farther than 10 parsecs away, while star B (which seems bright (m) but is actually dim (M) when placed at 10 parsecs away) must be located nearer than 10 parsecs, such that it is not possible for these two stars to located the same distance away from Earth; or instead
  2. in order for star A and star B to both be located closer than 10 parsecs (or farther away than 10 parsecs), then both their apparent magnitudes (m) must be brighter (dimmer) than their respective absolute magnitudes (M). Since this is not true, then it is not possible for these two stars to located the same distance away from Earth, as they cannot be both be closer or farther away than 10 parsecs.
• 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. At least discussion demonstrates understanding of relationships between apparent magnitudes, absolute magnitudes, and distances.
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. At least attempts to use relationships between apparent magnitudes, absolute magnitudes, and distances.
• x:
  Implementation/application of ideas, but credit given for effort rather than merit. Discussion based on garbled definitions of, or not based on proper relationships between apparent magnitudes, absolute magnitudes, and distances.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.

Grading distribution:
Section 30674
Exam code: midterm02N4ra
p: 27 students
r: 4 students
t: 3 students
v: 4 students
x: 0 students
y: 0 students
z: 0 students

Section 30676
Exam code: midterm02s0Ju
p: 34 students
r: 9 students
t: 6 students
v: 0 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 4354):

Astronomy quiz archive: Milky Way, cosmology

Astronomy 210 Quiz 7, spring semester 2015
Cuesta College, San Luis Obispo, CA

Sections 30674, 30676 version 1
Exam code: quiz07Ctlu


Section 30674

0- 8.0 :
8.5-16.0 :	***** [low = 9.5]
16.5-24.0 :	***********
24.5-32.0 :	************* [mean = 24.8 +/- 7.9]
32.5-40.0 :	******* [high = 40.0]

Section 30676

0- 8.0 :	** [low = 6.5]
8.5-16.0 :	*******
16.5-24.0 :	********** [mean = 23.9 +/- 8.5]
24.5-32.0 :	******************
32.5-40.0 :	******* [high = 40.0]

Physics midterm problem: comparing voltmeter readings

Physics 205B Midterm 2, spring semester 2015
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 18.72

Two voltmeters are connected to circuit with a switch, a light bulb, a resistor, and an emf source. All of these components are ideal. The resistance R of the resistor is greater than the resistance r of the light bulb. The top and bottom voltmeters have the same reading while the switch is open. Discuss why the top and bottom voltmeters will have different readings after the switch has been closed. Show your work and explain your reasoning using Kirchhoff's rules, Ohm's law, and properties of voltmeters.

Solution and grading rubric:

• p:
  Correct. Understands that closing the switch would allow current to flow through the emf, resistor and light bulb series circuit, while completely by-passing the lower voltmeter, such that:
  1. the upper voltmeter would read a non-zero voltage difference of ΔV = +ε – I∙R (or equivalently, ΔV = (–)I∙r); and
  2. the lower voltmeter would read zero, as there is no voltage drop due to the ideally zero resistance switch.
• r:
  Nearly correct, but includes minor math errors. Understands that current will now flow through the circuit, but does not give correct reading of one of the voltmeters, but has correct reading for the other.
• t:
  Nearly correct, but approach has conceptual errors, and/or major/compounded math errors. Understands that current will now flow through the circuit, but does not give correct readings for both voltmeters.
• v:
  Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner. At least understands that current will now flow through the circuit.
• x:
  Implementation of ideas, but credit given for effort rather than merit. Approach other than that of applying Kirchhoff's rules, Ohm's law, and properties of voltmeters.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.

Grading distribution:
Sections 30882, 30883
Exam code: midterm02m3tR
p: 8 students
r: 15 students
t: 7 students
v: 14 students
x: 3 students
y: 0 students
z: 0 students

A sample "p" response (from student 9178):

Physics quiz archive: magnetism, induction

Physics 205B Quiz 6, spring semester 2015
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz06t3SL



Sections 30882, 30883 results

0- 6 :	**   [low = 3]
7-12 :	*********
13-18 :	***************   [mean = 17.8 +/- 6.2]
19-24 :	****************
25-30 :	****   [high = 30]