
What Is Electricity? (2013) - calinf
https://learn.sparkfun.com/tutorials/what-is-electricity/
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lilgreenland
I teach high school physics. Here's my notes/textbook on electricity with
simulations and equations rendered in LaTex.

[https://landgreen.github.io/physics/notes/circuits/electrici...](https://landgreen.github.io/physics/notes/circuits/electricity/index.html)

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montecarl
Awesome notes. I haven't had my coffee yet so perhaps I'm just misreading this
part:

"In 1746 Benjamin Franklin mistakenly assigned a negative value to the charge
carriers that we now call electrons."

Shouldn't that read "mistakenly assigned a _positive_ value to the charge
carriers that we now call electrons"?

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lilgreenland
Nope! It's kinda silly. We all call electrons negative because of how they
were labeled 250 years ago. If he had labeled them positive the math involving
electric current would be a bit easier.

[https://xkcd.com/567/](https://xkcd.com/567/)

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esmi
I’ve been hearing for years that the math involved would be easier if we
switched signs on the electron but what equation specifically would be
simpler? One would still have to deal with both polarities. I tutored
electrical engineers for years and the biggest misconception by far was always
considering the amount (or movement) of charge and the number of particles to
be equivalent. Polarity was never really an issue.

~~~
lilgreenland
A couple things off the top of my head from teaching high school physics:

It would make the direction of current the same as the flow of charge.

It would make electric fields predict the force on electrons.

It would make the right-hand rule for magnetic fields work for electrons and
instead of the left-hand rule.

~~~
esmi
But existing theory predicts all those just fine, it just happens that some
things are not in the same direction, but it’s not like one can ignore
direction. The math is still always there. And I argue things going in
different directions is a feature, not a bug, because it reinforces the point
that net charge and net particles are not the same thing.

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SiVal
Right, the math is the same. We face this in physics all the time. You drop a
ball and it accelerates downward. Should the distance it covers be a negative
number? Well, it seems linear distance should be positive, but if it is, then
does down become positive? Shouldn't up be positive? Or do we reverse from
end-minus-start and make it start-minus-end?

It doesn't matter. The math is all the same with just different labeling
conventions.

For the general physics of electric charges, the convention that a proton is
+1 and electron is -1 is somewhat useful as a reminder of the larger range of
phenomena: protons carry charge, too, and a movement of positively charged
molecules makes the charge carriers and current move in the same direction.

But as soon as you start working with practical, artificial electrical
circuits (as opposed to, say, neurons), the electron-is-negative is a
nuisance, because the charge carriers are almost always simple electrons. To
visualize "stuff" moving one way, you have to visualize "other stuff" moving
the opposite direction. You have to keep thinking that when you add more you
get less. Visualization of electric/electronic technology would have been a
lot more convenient if the convention had been that electrons were positive,
protons negative.

~~~
esmi
We're probably going to have to agree to disagree on this one as I just don't
see the nuisance and I see some positive aspects to the existing convention
which I highlighted previously.

The classic, and really intuitive, experiment that requires one to understand
the movement of both the carriers and the charge at the same time is the
Haynes Shockley experiment [1]. It has not been my experience that charge
convention gets in the way of students interpreting this experiment.

For the vast majority of practical (artificial?) electronics, when designing
one only needs to look at the movement of net charge. Passive sign convention
(used by spice) is about the flow of charge, not carriers. Maxwell's equations
don't even mention the carriers. It's not clear to me why one needs to
visualise carriers to design circuits. In my experience (i.e. transmission
lines) it can actually hinder students to consider the movement of carriers
when designing a practical circuit.

[1]
[https://en.wikipedia.org/wiki/Haynes–Shockley_experiment](https://en.wikipedia.org/wiki/Haynes–Shockley_experiment)
[2]
[https://en.wikipedia.org/wiki/Passive_sign_convention](https://en.wikipedia.org/wiki/Passive_sign_convention)

~~~
SiVal
artificial: "made or produced by human beings rather than occurring naturally"

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javajosh
One aspect of electricity I think is useful to emphasize is that electrons in
a conductor move more like the steel balls Newton's cradle (that toy you may
have seen where a ball strikes one end of a line of balls, and nothing moves
except the end ball, or you can pull back two balls and then only two balls
will move, and so on). This can help with intuition about the distinction
between "holes" and electrons, and how energy can flow with holes (which is
quite counter-intuitive, I think). In terms of mental model, the _ratio_ of
holes to ambient electrons is sometimes useful to think about, as this is
fundamental to computing current limits of conductors.

There is a diagram (an animated GIF) about half-way down that sort of implies
the newton's cradle method of moving charge, but I don't like it because it's
not clear enough. Also, I see current as more of a fixed cloud of valence
electrons with holes moving through it - which is a very different intuition
than what this diagram implies.

~~~
lilgreenland
Here's my take on a cartoony conductivity simulation. I've got three models:
conductors, semiconductors, and semiconductors but with holes.

[https://landgreen.github.io/physics/notes/electromagnetism/c...](https://landgreen.github.io/physics/notes/electromagnetism/charge/index.html#conductivity)

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dreamcompiler
I like these diagrams. Now I want to see what superconductivity looks like in
your framework. An unimpeded stream of electrons flowing as if the red dots
aren't even there?

~~~
lilgreenland
My simulation just runs classical physics (Coulomb's law + Newton's laws).
It's missing any mechanism for super conductivity. Although, I could just turn
off friction.

I think superconductivity means the electrons pair up and stop colliding
through the Pauli exclusion principle. I didn't code any collisions, so maybe
it's already modeling a crappy version of superconductivity!

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negamax
Just amazing! Imagine all the physics and knowledge from multiple sciences,
disciplines and fields are used when someone tells Amazon Echo to turn on a
charger or socket that’s connected to a phone or laptop.

Echo -> ISP wires —> Undersea Cables —> Amazon Servers -> Back home ->
Electricity flow

And this is so super high level

All of these devices on the way are powered by electricity from dams, solar,
wind etc. Before voice to speech hits or data is read. Processors and hard
disks must do so much heavy lifting

It’s surreal the level of abstraction we are surrounded by..

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aaronblohowiak
Quite fascinating and mind-boggling. What really blows my mind is that
technology is still extraordinarily less complicated than (bi|ec)ology.

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dang
A thread from 2015:
[https://news.ycombinator.com/item?id=10400123](https://news.ycombinator.com/item?id=10400123)

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geggam
It's interesting to me when I read it. We take it down to the proton neutron
and electron stating they are charged with positive negative or neutral
charge.... but what are they charged with ?

Electricity ? What is it made of ?

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dreamcompiler
It's made of the electromagnetic force. We can measure it and characterize it
very accurately with mathematics. We can say what it _isn 't_ (gravity or the
weak force or the strong force), but we cannot say what the electromagnetic
force _is_. Sorry. If you figure it out you'll get a Nobel Prize.

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rnestler
> We can say what it isn't (gravity or the weak force or the strong force)

Isn't the electric and the weak force considered the same force these days?
See also
[https://en.m.wikipedia.org/wiki/Electroweak_interaction](https://en.m.wikipedia.org/wiki/Electroweak_interaction)

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carapace
For an exercise in clear (and perhaps provocative) thinking, try:

'What Is "Electricity"?' ©1996 William J. Beaty

> What is electricity? This question is impossible to answer because the word
> "Electricity" has several contradictory meanings. These different meanings
> are incompatible, and the contradictions confuse everyone. If you don't
> understand electricity, you're not alone. Even teachers, engineers, and
> scientists have a hard time grasping the concept.

> Obviously "electricity" cannot be several different things at the same time.
> Unfortunately we've defined the word Electricity in a crazy way. Because the
> word lacks one distinct meaning, we can never pin down the nature of
> electricity. In the end we're forced to declare that there's no such stuff
> as "electricity" at all!

[http://amasci.com/miscon/whatis.html](http://amasci.com/miscon/whatis.html)

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Koshkin
Analyzing the meaning of words is characteristic to philosophy and is not a
sign of “clear thinking.”

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HNLurker2
This is trivial for somebody who studies electrical engineering in highschool

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kalado
Basic introductions of a topic are trivial for people that are studying that
topic? Shocking!

