1. Craig Ogilvie 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. Craig Ogilvie 2 Gains “active engagement” improves conceptual understanding “Gain” = fraction of possible improvement, traditional active R.R. Hake, Force Concept Inv. Am. J. Phys. 66, 64- 74 (1998) gain

3. Craig Ogilvie 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 –Johnson 2 (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. Craig Ogilvie 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. Craig Ogilvie 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 moving charge 1 generates B-field moving charge 2 experiences force in B-field This symmetry is a key part of a coherent picture of B-fields

6. Craig Ogilvie 6 B-field From Moving Charge (Movie) http://www4.ncsu.edu/~rwchabay/emimovies/ Ruth Chabay

7. Craig Ogilvie 7 B-field From a Moving Charge  Observations over the years –stronger B-field if q larger, and if v larger –B-field decreases with distance (r) from the moving source B-field is circular!!! around moving charge e.g. charge (q>0) moving into screen with velocity v

8. Craig Ogilvie 8 B-Field From Moving Charge, Biot-Savart vv rr P rr direction of B-field at point P Take your right hand 1)point fingers in direction of  v 2)curl fingers towards  r 3)thumb gives  v  r

9. Craig Ogilvie 9 Question  What is the direction of the B-field at point P ?  v q >0 P A) B)C)D) 1) Work individually 2) Commit when I ask 3) Work in pairs 4) Commit when I ask

10. Craig Ogilvie 10 Question  What is the direction of the B-field at point P ?  v q >0 P A) B)C)D) vv rr  r is from charge to point P

11. Craig Ogilvie 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, don’t 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. Craig Ogilvie 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. Craig Ogilvie 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 ? i P A) B)C)D) e - move opposite to i,  e - down wire consider single electron vv rr since q <0,  B opposite direction as out of screen for all electrons in wire

14. Craig Ogilvie 14 B-field Due to Straight Line Current  B-field at P  Each current element gives dB into screen  dB decreases 1/ r 2  Integrate from -  to + 

15. Craig Ogilvie 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 P R R i i

16. Craig Ogilvie 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. Craig Ogilvie 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. Craig Ogilvie 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