Physics quiz archive: interference, electrostatics

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



Sections 30882, 30883 results

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

Physics quiz archive: magnetism, induction

Physics 205B Quiz 6, spring semester 2019
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz06riQ1



Sections 30882, 30883 results

0- 6 :
7-12 :	***** [low = 9]
13-18 :	********
19-24 :	************** [mean = 21.4 +/- 5.5]
25-30 :	*********** [high = 30]

Physics quiz archive: magnetism, induction

Physics 205B Quiz 6, spring semester 2018
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz06Av3g


Sections 30882, 30883 results

0- 6 :	* [low = 6]
7-12 :
13-18 :	************
19-24 :	******************* [mean = 20.1 +/- 4.2]
25-30 :	** [high = 27]

Physics quiz archive: interference, electrostatics

Physics 205B Quiz 3, spring semester 2019
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz03b3Am



Sections 30882, 30883 results

0- 6 :	** [low = 3]
7-12 :	**
13-18 :	*********
19-24 :	***************** [mean = 21.5 +/- 6.0]
25-30 :	************ [high = 30]

Physics quiz archive: interference, electrostatics

Physics 205B Quiz 3, spring semester 2018
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz03Ch4R



Sections 30882, 30883 results

0- 6 :
7-12 :	** [low = 9]
13-18 :	****
19-24 :	************ [mean = 23.3 +/- 4.9]
25-30 :	************** [high = 30]

Physics quiz archive: magnetism, induction

Physics 205B Quiz 6, spring semester 2017
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz06LnDr


Sections 30882, 30883 results

0- 6 :
7-12 :
13-18 :	******** [low = 15]
19-24 :	************** [mean = 21.8 +/- 4.1]
25-30 :	******* [high = 30]

Physics quiz archive: interference, electrostatics

Physics 205B Quiz 3, spring semester 2017
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz03d3St



Sections 30882, 30883 results

0- 6 :
7-12 :	* [low = 9]
13-18 :	*****************
19-24 :	******** [mean = 18.6 +/- 4.4]
25-30 :	** [high = 27]

Physics quiz archive: magnetism, induction

Physics 205B Quiz 6, spring semester 2016
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz06eL3k



Sections 30882, 30883 results

0- 6 :	*   [low = 6]
7-12 :	*****
13-18 :	*********************   [mean = 17.0 +/- 5.1]
19-24 :	**********
25-30 :	*   [high = 27]

Physics quiz archive: interference, electrostatics

Physics 205B Quiz 3, spring semester 2016
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz03Ccf7



Sections 30882, 30883 results

0- 6 :	** [low = 6]
7-12 :	***********
13-18 :	******
19-24 :	*************** [mean = 18.8 +/- 7.2]
25-30 :	****** [high = 30]

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]

Physics quiz archive: interference, electrostatics

Physics 205B Quiz 3, spring semester 2015
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz03wJnb



Sections 30882, 30883 results

0- 6 :	****** [low = 0]
7-12 :	*****
13-18 :	****************** [mean = 16.7 +/- 7.2]
19-24 :	***********
25-30 :	**** [high = 30]

Physics final exam question: direction of induced current

Physics 205B Final Exam, spring semester 2014
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 20.27

The current in a circular loop is decreasing over time. A square metal loop (with a resistance R) is located alongside the circular loop. Discuss why the direction of the induced current in the square metal loop is clockwise. Explain your reasoning using the properties of magnetic fields, magnetic flux, Faraday's law and Lenz's law.

Solution and grading rubric:

• p:
  Correct. Uses (1) right-hand rules to determine that magnetic flux caused by the circular loop is directed into the page through the square loop; discusses (2) how decreasing current in the circular loop then creates decreasing magnitude flux that points into the page through the square loop; and concludes (3) from Faraday's and Lenz's laws that the changing flux induces a current in the square loop that will supplement the decreasing magnitude flux that points into the page, and thus be clockwise.
• 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 argument has conceptual errors, or is incomplete.
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Some attempt at using right-hand rules, magnetic fields, forces, currents, flux, Faraday's (and Lenz's) law, induced emf and induced current.
• x:
  Implementation/application of ideas, but credit given for effort rather than merit.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.
  

Grading distribution:
Sections 30882, 30883
Exam code: finalEL7a
p: 13 students
r: 4 students
t: 8 students
v: 5 students
x: 5 students
y: 0 students
z: 0 students

A sample "p" response (from student 0115):
A sample "x" response (from student 4297), with at least some rudimentary representation of Lenz's law:

Physics quiz question: loop alongside loop with increasing current

Physics 205B Quiz 6, spring semester 2014
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 20.27(a)

The current in a circular loop is increasing over time. A square metal loop (with a resistance R) is located alongside the circular loop. The direction of current induced in the square loop is:
(A) clockwise.
(B) counterclockwise.
(C) (No direction, as there is no induced current.)
(D) (Not enough information is given.)

Correct answer (highlight to unhide): (A)

The circular loop is the source of an external magnetic field that creates a flux through square loop, which is the considered the test object. Since the current in the circular loop is increasing, its magnetic field and magnetic flux through the square loop will increase over time, which will create an induced current in the square loop according to Faraday's law.

Everywhere inside of the circular loop, its clockwise current will create a magnetic field that points into the page. Everywhere outside of the circular loop, its current will create a magnetic field that points out of the page. This magnetic field will create a magnetic flux that points out the page through the square loop.

The external magnetic flux through the square loop that points into the page is increasing over time, and from Lenz's law, a current is induced in the square loop that will oppose this change. The square loop will then attempt to create its own magnetic field that points into the page, which means that the induced current in the square loop will be clockwise.

Sections 30882, 30883
Exam code: quiz06Lp4s
(A) : 9 students
(B) : 24 students
(C) : 3 students
(D) : 0 students
(No response: 1 student)

Success level: 24%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.28

Physics quiz archive: magnetism, induction

Physics 205B Quiz 6, spring semester 2014
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz06Lp4s



Sections 30882, 30883 results

0- 6 :	* [low = 6]
7-12 :	******
13-18 :	**************** [mean = 17.8 +/- 5.4]
19-24 :	***********
25-30 :	** [high = 30]

Physics quiz archive: interference, electrostatics

Physics 205B Quiz 3, spring semester 2014
Cuesta College, San Luis Obispo, CA
Sections 30882, 30883, version 1
Exam code: quiz03cDvD



Sections 30882, 30883 results

0- 6 :
7-12 :	*** [low = 9]
13-18 :	*******************
19-24 :	************* [mean = 19.7 +/- 5.0]
25-30 :	***** [high = 30]

Physics quiz archive: magnetism, induction

Physics 205B Quiz 6, spring semester 2013
Cuesta College, San Luis Obispo, CA
Section 30882, version 1
Exam code: quiz06h4cK



Section 30882 results

0- 6 :
7-12 :	*** [low = 12]
13-18 :	*********
19-24 :	************* [mean = 20.8 +/- 5.4]
25-30 :	******* [high = 30]

Physics quiz archive: interference, electrostatics

Physics 205B Quiz 3, spring semester 2013
Cuesta College, San Luis Obispo, CA
Section 30882, version 1
Exam code: quiz03rD1o



Section 30882 results

0- 6 :
7-12 :	****** [low = 9]
13-18 :	********
19-24 :	************* [mean = 19.9 +/- 5.5]
25-30 :	***** [high = 30]

Physics quiz question: loop pulled across magnetic field threshold

Physics 205B Quiz 6, spring semester 2012
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Example 20.1

A square metal loop (of resistance R) moves at constant velocity. An external magnetic field has uniform magnitude and direction in a certain region, and is zero everywhere outside of this region. The direction of current induced in the square loop is:
(A) clockwise.
(B) counterclockwise.
(C) (No direction, as there is no induced current.)
(D) (Not enough information is given.)

Correct answer (highlight to unhide): (C)

Since the magnetic flux Φ_B through the square metal loop does not change over time, there will be no induced emf and no induced current in the loop. (Alternatively, positive charges in both the left and the right sides of the loop experience upwards forces, but these induced clockwise and counterclockwise currents will effectively cancel out, leaving no net induced current in the loop.)

Section 30882
Exam code: quiz06LR1r
(A) : 12 students
(B) : 10 students
(C) : 5 students
(D) : 0 students

Success level: 19%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.38

Physics quiz question: induced emf in inductor

Physics 205B Quiz 6, spring semester 2012
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 20.55

An ideal emf source is connected to an ideal resistor and inductor. The switch is closed at t = 0. Just after t = 0, the __________ side of the inductor is at a higher potential.
(A) left.
(B) right.
(C) (There is a tie.)
(D) (Not enough information is given.)

Correct answer: (B)

Just after the switch is thrown at t = 0, increasing current will flow through the inductor from right-to-left. The resulting induced emf in the inductor will oppose this increasing current, resulting in the right side of the inductor being at a higher potential.

Section 30882
Exam code: quiz06LR1r
(A) : 10 students
(B) : 15 students
(C) : 2 students
(D) : 0 students

Success level: 56%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.58

Physics quiz archive: magnetism, induction

Physics 205B Quiz 6, spring semester 2012
Cuesta College, San Luis Obispo, CA

Section 30882, version 1
Exam code: quiz06LR1r

Section 30882 results
Quiz 6 results (max score = 30):

0- 6 :
7-12 :	** [low = 12]
13-18 :	*****
19-24 :	************* [mean = 22.0 +/- 4.9]
25-30 :	****** [high = 30]