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Re: [Phys-l] Movie Physics Gafs



It is nice that such workshops are held, and the elementary teachers need to
understand magnetism to be able to have the students explore it.

Minds on Physics just has students first interact with magnets, and then
look a labeled magnet to see which end points N. Then they are asked what
end of a magnet is at the N pole. I think that the terminology N seeking is
actually confusing, and just using N and S provides cognitively lower load.
The big problem is that students want to label the ends of magnets as + and
-, which again plays into the misconception that electrical and magnetic
forces are the same.

John M. Clement
Houston, TX


Back in the days of giving summer workshops for
teachers I bought a supply of brass pins (for
NON-magnetic items) and el cheapo compasses from
Oriental Trading for general magnetic stuff.

The 'brass' pins turned out to be brass plated
steel and the compasses all had aluminum needles
! ! !

I had the joy of 'correcting' the polarity of our
Sargent Welch re-magnetizer box as well.

(When was it that the physics books stopped
labeling the N end of a compass as the 'North
SEEKING' pole!!!!) grrr. I remember Dull Metcalf
and Williams doing this back in the bad-old-days)

I started hanging a bar magnet from the light
fixture and asking students (and fellow teachers)
which end would point towards Santa Claus. (or
Canada - for the non-believers)
.
At 1:43 PM -0500 9/12/11, John Clement wrote:
This misconception is well documented by PER
researchers, so one should not be surprised.
The Minds on Physics series very sensibly covers
all of the long range non contact forces in one
section. So students are exposed to
electrostatic, magnetic, and the general
gravitational law all at once. The distinction
between how the forces are produces is clearly
exposed. So in testing for understanding
questions are asked that reveal whether the
confusion between electrical, magnetic, and
gravitational forces is present. There is one
school educational website that talks about
magnetic interactions as if it were electrical
in nature and uses terms which I consider are
designed to promote this misconception.

If you want to find out what students think just
ask "What can magnets pick up?" and they will
almost invariably say "metals". MOP has them
actually test a variety of materials such as
aluminum, steel, copper, their own jewelry...
This has not been done in the lower grades, so
they are severely misconcepted about how magnets
work.

But when this sort of thing is put into
commercial movies, you know that the directors
don't know simple physics either.

John M. Clement
Houston, TX


Here is a video showing a compass made from a needle
magnetized with a silk cloth!


http://www.youtube.com/watch?v=wIGbNJDYdnM&feature=player_detailpage


From: Bob Sciamanda
Sent: Monday, September 12, 2011 10:00 AM
To: Forum for Physics Educators
Subject: [Phys-l] Movie Physics Gafs
I just watched ⤦The Edgeâ¤ù (1997, Anthony Hopkins,
Alec Baldwin).
Lost in the wild, Hopkins (playing a very knowledgeable
outdoorsman) makes a compass by floating a needle on a leaf.

But he ⤦magnetizesâ¤ù the needle by rubbing it with a
piece of silk!


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