Student Learning in Large Science Lectures

1
Student Learning in Large Science Lectures

• Many quantitative studies of how much students
  learn in physics classes
• Physics concept exams taken pre and post
  instruction
• repeated at many colleges/universities
• Comparison between
• traditional lecture
• monologue, interspersed with Q/A, demonstrations
• interactive lectures
• pair discussions, short multiple choice, student
  written summaries,.

2
Gains
traditional
active
R.R. Hake, Force Concept Inv. Am. J. Phys. 66,
64- 74 (1998)
gain

• active engagement improves conceptual
  understanding

3
My Experience

• Most students get lost at some point in a
  traditional lecture
• once lost, they stop taking notes, fall asleep,
• In-class activities allows students to catch-up
• Many active possibilities, whole books written
  on topic
• Johnson2(Active Learning), Marzano ( Classroom
  Instruction), MacGregor (Strategies for
  Energizing Large Classes), Mazuur (Peer
  Instruction)
• Common characteristics
• designed so that all students participate
• students first work on task by themselves, then
  in pairs
• accountability
• feedback so students can check their
  understanding

4
Goals for Today

• Example interactive work in a class
• Wonders of Magnetic Fields
• Magnetic (B) fields produced by moving charges
• Practice with direction of B-fields

5
B-Field from Moving Charge

• Baseline info a moving charge experiences force
  in a B-field
• How did the B-field get created in the first
  place?
• first step in understanding fridge-magnets,
  maglev trains
• B-fields are made by moving charges

This symmetry is a key part of a coherent picture
of B-fields
6
B-field From Moving Charge (Movie)
Ruth Chabay
http//www4.ncsu.edu/rwchabay/emimovies/
7
B-field From a Moving Charge
B-field is circular!!! around moving charge
e.g. charge (qgt0) moving into screen with
velocity v

• Observations over the years
• stronger B-field if q larger, and if v larger
• B-field decreases with distance (r) from the
  moving source

8
B-Field From Moving Charge, Biot-Savart

• Take your right hand
• point fingers in direction of ?v
• curl fingers towards ?r
• thumb gives ?v ??r

9
Question

• What is the direction of the B-field at point P ?

P
?v q gt0
A) B) C) D)
1) Work individually 2) Commit when I ask 3) Work
in pairs 4) Commit when I ask
10
Question

• What is the direction of the B-field at point P ?

P
?v q gt0
A) B) C) D)
11
Types of Question

• Previous example was a check of student
  understanding immediately after topic was
  presented
• gives students chance to catch up
• provides feedback to students
• provides feedback to instructor on how much
  students understood
• Typical question, 60-70 get it correct first
  time
• if 90 get it right, dont go through pair
  discussion
• Percentage of correct answers often improves to
  90 after pair-discussion
• Another type of question, ones that lead into
  new area

12
Question

• For the very long wire carrying a current i in
  the direction shown, what is the direction of the
  B-field at point P ? (use Biot-Savart law)

i
P
A) B) C) D)
13
Question

• For the very long wire carrying a current i in
  the direction shown, what is the direction of the
  B-field at point P ?

• e- move opposite to i,
• e- down wire
• consider single electron

i
P
?r
?v
out of screen for all electrons in wire
since q lt0, ?B opposite direction as
A) B) C) D)
14
B-field Due to Straight Line Current

• B-field at P
• Each current element gives dB into screen
• dB decreases 1/ r2
• Integrate from -? to ?

15
Strategy Question

• From the two very long wires separated by R, how
  would you find the direction and magnitude of the
  B-field at point P ?
• Write down your strategy on how to solve this
  problem
• include thoughts on
• when this strategy can be used
• why this strategy may be useful
• Share with neighbor
• Class list

16
Pros/Cons

• Write down what you see as the pros/cons of
  interspersing lectures with these types of
  questions
• Compare your list with neighbor
• Class List

17
Higher-Level Questions

• Previous question asked for a synthesis of
  information
• pros/cons
• similarities/differences
• Venn diagrams
• .
• What similar experience do others have?

18
Summary

• B-fields generated by moving charges
• Direction of B-field, circular around the moving
  charge
• Multi-choice questions, strategies, comparisons,
  pros/cons, end-of-lecture summaries, muddiest
  points,
• Regular active periods in a lecture
• designed so that all students participate
• students first work on task by themselves, then
  in pairs
• accountability
• provides feedback to students and instructor
• Data shows student learning increases