Re: [Phys-l] Challenge Activity

[John Denker <jsd@av8n.com>]

On 01/21/2009 07:26 PM, Arts, Robert W. wrote:

> This term I'm trying to add some new elements to the Physics II lab
> experience.  I plan on covering two labs related to a section of
> material then conducting a "challenge activity" during the next lab
> period.  For example, after covering circuits and resistance, the
> challenge activity will be a black-box electric circuit that they
> have to figure out the wiring diagram for based on the information
> they obtained from their previous laboratory experiences.  No direct
> instructions will be given for the challenge beyond the goal they are
> to accomplish.  At the end of the lab period they will submit a
> journal of their investigations along with a short write-up of their
> conclusions.  Okay...my question...might anyone have an idea for a
> challenge-type activity for vibrations, waves, & sound and for
> magnetism?  I have the one for circuits (as mentioned) and one for
> light & optics but am at a loss for the other two topics.

I heartily encourage you to go down this road ... but you need 
to do it carefully.

I assume this is a college course for non-majors;  if not, please 
clarify.

I apologize for not directly answering the question that was asked,
but I do have some possibly-constructive suggestions (see below).

But first, there are some other issues that cry for attention.
 -- Are you sure these kids are ready for high-level open-ended
  challenges?  You know the kids, and I don't, but it's not 
  something you can take for granted.

  Some schools prepare kids for this sort of thing, but many
  schools don't.  You might have to lay a huge amount of
  groundwork.  You can't just throw them into the deep end
  and say "swim!"

>  ... No direct instructions will be given  ...


This is the crux of the problem, since kids are not accustomed
to open-ended questions.  This is something that needs to be 
learned and needs to be taught.  It is possible and highly
commendable but not easy.  At first the kids won't even understand 
what you are asking, and if/when they understand you they won't 
believe you.  They've been trained for years that in school, 
rote regurgitation is rewarded and thinking is punished.  You 
cannot undo all that overnight.

Part of the trick is to make the "challenge" challenging enough 
so that kids get a feeling of accomplishment from completing the
challenge, yet easy enough that even the not-so-brilliant ones can 
get some traction on it.  It is wicked hard to get this right;  
you can just as easily miss low as miss high.

Sometimes "challenging" is used as euphemism for "difficult" but
I assume that's not the objective here.  I assume that _open-ended_
is the crux.  So we are looking for problems that are open-ended
but not unduly hard.  Preferably not hard at all, just open-ended.

I worry that a black-box electronics challenge may be too advanced
to serve as a starting point, in part precisely because they can't 
see into the black box, and in part because the result is likely to 
be all-or-nothing: either they get it or they don't.  In contrast, 
I would be tempted to start with something like the "paper tower" 
challenge.
  http://www.google.com/search?q=paper-tower+challenge

The paper tower challenge has several advantages: 
 a) partial success is rewarded;  everybody gets to build _something_
 b) there are no secrets;  everybody can see how the winner did it.
 c) there is an unlimited upside;  even the winners will be wondering
  if they could have done better.
 d) it is a very "active" activity.  very hands-on.
 e) there is plenty of physics in it:  leverage, metastability, margin
  of stability, basic geometry, symmetry, and strategy.  Sophistication
  is rewarded.
 f) The competitive aspect is instant motivation for a certain subset 
  of the population.

I also heartily recommend assigning some Bongard problems as a
warm-up exercise.  They are open-ended, with an impressive variety
of answers ... and kids enjoy them.

Jearl Walker _The Flying Circus of Physics_ is a valuable source of
open-ended questions of varying level of difficulty.

More possibly-constructive suggestions can be found at
  http://www.av8n.com/physics/thinking.htm

=============================

To actually answer the question that was asked would require some
additional information.  Much depends on what resources are available,
and what additional resources can be obtained.
 -- Is this a lab course?  Do you have plain old lab _space_ for
  each student, i.e. a few square feet they can call their own
  for the duration ... or does everything have to be torn down 
  and cleaned up at the end of the hour?
 -- Do you have at least one oscilloscope for every two or three
  students?  Power supplies?  Computers?  Power amplifiers?
  Hand tools?  Power tools?  Baling wire?

These questions seem relevant because most of the "challenges"
I can think of take time, space, and/or equipment.  For instance,
making an electric motor from scratch is the most interesting
thing you can do with magnets ... but it's not something a student 
could do in an hour.  (I could do it in an hour, using nothing
but coathangers, magnet wire, and tape ... but I'm not taking
the class.)  Have a contest for the highest no-load speed,
highest starting torque, et cetera.

Similarly a fun thing to do involving electrostatics is to 
build an electrostatic generator.  A Kelvin water-dropper is,
as Mr. Spock would say, crude but effective.  Also amazingly
messy (which students are not expecting, and may find amusing).  
To make it more of a challenge, turn it in to a contest for 
the highest open-circuit voltage, highest current*voltage 
product, et cetera.

   Avoid Leyden jars and especially Leyden-jar contests.  Too
   dangerous.

A more advanced "magnet" challenge is to MacGyver a jig that 
measures B and H simultaneously in some material, and plots the 
hysteresis loop on a scope.