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Re: coulombs




Here's a perspective on I vs Q which I've yet to encounter anywhere.
Opinions?

The ampere is far easier to measure with precision than is the coulomb.
The second is easy to measure. Therefor, the ampere and second are
measured, and the coulomb is derived.

This concept cuts all through educational materials, but it appears in a
twisted form: that current is "real" and charge is not.

It appears in elementary school books, where it is claimed that "quantity
of electricity" is measured in amperes.

It appears in higher-level texts where students are taught first about
current, and only later (if at all) about the substance which does the
flowing.

It subtly appears all through non-science electronics texts, where authors
focus on current, on amperes, and only mention the flowing "substance" in
passing.

It appears in the widespread conviction that charge is not like a
substance.

I was long confused about the origin of all these misconceptions, but
recently have become convinced that our method of standardizing physical
units is the cause. The origin of the misconceptions is the fallacy that
amperes are more fundamental than coulombs, where the word "fundamental"
is
used in a popular sense, rather than with a specialized meaning pertaining
to physical units, as in "fundamental" versus "derived."

So, in the everyday world, and using a popular meaning of "fundamental,"
conserved quantities are more fundamental than rates. For example, kg are
more fundamental than kg/second, cc's are more fundamental than cc/sec,
meters are more fundamental than meters/sec, joules are more fundamental
than watts.

But in electricity, the opposite is believed, that amperes are a
fundamental unit, and that coulombs are a hard-to-understand concept
involving ampere-seconds.

I say, on the contrary. Coulmbs are "fundamental," while amperes are just
a convenient simplification of the concept "coulombs per sec." And, while
this violates the concept "fundamental vs derived" it is more correct than
the reverse, and I believe that it makes much more sense to the
inexperienced learner.

Now, how does one convince a textbook publisher to take this idea
seriously, when he/she can open a physics book and find statements saying
"amperes are the fundamental unit."

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