Re: POSITIVE AND NEGATIVE

[Jack Uretsky <jlu@HEP.ANL.GOV>]

        Well, yes.  As I pointed out at a meeting at UIC last year on
improving teaching (of physics, as I recall) everybody and his dog wants
to invent his own physics course, but nobody wants to discuss and
collaborate.   I am probably guilty on the first count, but I am firmly
resistive on the second.
        The E&M Labs that I am posting were created to be discussion labs,
modeled on those that Hake did for mechanics.  The test of their success
is the extent to which they can be used to promote discussion and "aha!"
experiences.  They differ from what Kowalski and the "Seat Labs" do in
that the student is expected often to give answers that change as a result
of discussion.
        For example:  in my Lab1, question 1a:  Is there a force acting on
the tape or on the ball?  It is easy for the student to circle the Y and
go on.  That's not enough, so I mark the answer with a big, red "D" and
hand it back.  After some discussion (this is the first lab of the
quarter, so we start by forming good habits), someone gets the idea of
making a sketch of the setup using force vectors.  That's the kind of
answer that's wanted throughout the sequence.

        The Seat Lab question "How does the force vary with distance?" is,
in my mind, a loser unless you have some communicable way, that can be
shown with a sketch of what actually happens, of characterizing the
change.  And questions like "how many electrons?", totally miss the point
unless you have some way of verifying the count other than checking the
student's arithmetic.  The student (and, often, the teacher) has no
concept of what consititutes an electron and doesn't need to know, at this
point, that charge is quantized.
        My lab sequence has emphasized, through two quarters, the notion
of "operational definition".  It suffices, for this posting, to say that
an operationaly definition is a picture of someone doing something.  My
Lab1, then, gives an operational definition of the verb "to charge",
namely, a picture of a tape being pulled off of a table.
        In summary, there are cookbook labs and discussion labs.  Dick
Hake, as far as I know, invented the discussion labs and I've tried to
adapt them a extend them to E&M.  If you want to improve on them, try
them, first by yourself (to see what works and doesn't work - I guarantee
surprises), then on some students to see what promotes discussion.  If
that's not your agenda, then you're probably content with cookbooks.
                                        Regards,
                                                Jack


On Thu, 24 Jan 2002, Daniel L. MacIsaac wrote:

> > HERE IS THE CORRECTED VERSION. THANKS FOR CORRECIONS.
> >
> >                  DISCOVERING TWO KINDS OF CHARGES
> >                  **************************************
> >
> > Based on "Electric and Magnetic Interactions" (by R. Chabay and B. Sherwood.)
> > To be used by Ludwik Kowalski, at Montclair State University. Spring 2002
>
> See also:
>
> http://purcell.phy.nau.edu/SeatExpts/index/
> "Straw and pens"
> "Sticky tape"
> "Electrophorus"
>
> Dan M
>
> Dan MacIsaac, Assistant Professor of Physics and Astronomy, Northern AZ Univ
> danmac@nau.edu          http://purcell.phy.nau.edu         PHYS-L list owner

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