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Re: Meauring Volts?




I find that most of my HS physics don't really UNDERSTAND the difference
between the quantity being measured and the UNIT
for that quantity. Has this possibility been discussed, and I
missed it? Or is the possibility too ludicrous to consider?




This is exactly correct. Often college students have the same difficulty.
This difficulty of course happens in daily life. For example people will
say you need a certain square footage of shingles to cover your roof, or the
yardage of material is ...

While texts often use the proper terms, I have not seen much in the way of
text that actually discusses this particular linguistic problem. It is just
one of many linguistic problems that students have. A much more important
problem is their inability to distinguish between physical objects and
ideas. They will talk about force as something that you posses. There have
been some PER talks which propose that student difficulties mainly trace
back to being unable to make the proper linguistic distinctions. I think
that this is actually a sign of the overall confusion that students have
with physics ideas. This particular aspect of student problems has not
actually been well researched or treated by PER.

The physics texts mainly assume that students pick up correct usage by
example, and then proceed to give explanations using language that students
do not understand very well. One improvement in texts would be to
explicitly tell students some of these distinctions, or to have lessons
where students have to distinguish between names and units, between ideas
and physical objects.

Some of this is traceable to elementary schools where teachers ask students
what makes objects fall. They then proceed to tell them that it is caused
by gravity. They might just as well have said by magic!!! This sets up the
misconception that gravity is a "thing" rather than just a description that
things fall down. Now if they had left students to come up with their own
explanations and then used various techniques to expose problems with the
explanations, students would be much better off. Even saying that the earth
pulls them down would be somewhat better.

I would consider the unit vs quantity name problem to be minor compared to
the idea vs physical object problem. Getting students to say gravitational
force rather than gravity or force of gravity is much more important. Once
students begin to make the distinction between ideas and objects, I suspect
that the difference between units and names will probably be easily fixed.

Just grading their statements for correctness changes their behavior very
little. This is because the grade is usually so remote from the event that
it makes no impact on the students. Being careful about correct usage, and
explicitly pointing out what is correct probably has more effect. Perhaps
Bob Beichner should consider adding comments on language usage to his text.

John M. Clement
Houston, TX