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[Phys-L] Re: The bulb-with-one-wire task: too tricky?



I would guess that your grandchildren would be lucky since these
students now understand what guided inquiry is and how it works. Then
can also explain how a circuit works in ways that their boyfriend
electrical engineers cannot. They are surprised when they hear their
boyfriends saying things that they know are obviously wrong.
I don't think its fair, Herb, to criticize until you know more of what
is happening. If you were aware of the curriculum and had read my note
carefully you would have realized that this experience is the beginning
of their learning not the end.

cheers,

joe

Herbert H Gottlieb wrote:

Joe Bellina refers to his "preservice eleds" all of whom seem to
find great difficulty figuring out how to light a flashlight bulb
when given a battery and connecting wires. Is it possible that
these "eleds" are high school graduates who are close to being
graduated from a college ?

If so, what will happen to our country when they start teaching
our grandchildren???

Herb



On Tue, 22 Feb 2005 09:30:49 -0600 Joseph Bellina
<jbellina@SAINTMARYS.EDU> writes:


I don't think of this task as a test. It is rather a very good
engagement exercise. When my pre-service eleds do it, many go
through
three stages.
First, since most of them think of batteries and bulbs in terms of
a
tranfer or delivery, they connect the one wire to the bulb and to
the
battery and of course nothing happens.
Then they note that the battery has two ends and begin to think of
ways
to incorporate the two ends. Thats when they are likely to connect
the
wire directly across the battery.
By the way, to forestall the uncomfortable hot sensation they get at
the
battery wire connection I use somewhat worn out AA batteries, which
will
still light the bulb but won't deliver enough current to make the
connection hot.
Once the figure they can't light the bulb by making one connection
to
the bulb, I sometimes have to raise the question of whether or not
there
are two "ends" of the bulb just as there are two ends to battery and
to
the wire.
Eventually they find 4 different configurations to light the bulb,
but
for them them the bulb is still a black box. This is a very
instrumental exercise, if I may use this philosophical term, the
only
really new insight is that there is a need for some sort of
circulation.

Just for the record , this is McDermott's Physics by Inquiry.

I think several things are happening in this exercise. First the
students are getting comfortable with bulbs and wires and
batteries.
Second they are beginning to see that a delivery model does not
work,
but that their actions are predicated on it. They begin to see
that
they need to think in terms of a circulation model.
It is a good place to begin, but not a good test since so many
pieces
have to go together to be successful. By the way, seeing the bulb
light
is exciting for these students....so there is a nice reward for
success.

One other point. This year I gave a pretest that had a series of
pictures showing ways the bulb, wire, and battery might be
connected,
and asked them to predict which would light. The students got
about
half of them correct, with some configurations consistently wrong.
However, the pretest seemed to have no effect on their ability to
light
the bulb, because the process for the students was essentially the
same
as it had been when I didn't give the pretest. They didn't seem to
pick
up any clues for how to do it successfully, and it didn't even give
them
clues on different ways to connect the three pieces together.

cheers,

joe

--
Joseph J. Bellina, Jr. Ph.D.
574-284-4662, 4968
Saint Mary's College
Dept. of Chemistry and Physics
Notre Dame, IN, 46556






Herb Gottlieb from New York City
A friendly place to live and visit




--
Joseph J. Bellina, Jr. Ph.D.
574-284-4662, 4968
Saint Mary's College
Dept. of Chemistry and Physics
Notre Dame, IN, 46556