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What Is Electricity? (2013)

learn.sparkfun.com

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Re: What Is Electricity? (2013)

#21

Post by esmi »

lilgreenland wrote: post #15
montecarl wrote: post #13

Earlier quoted context omitted.

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"?

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/

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.

Re: What Is Electricity? (2013)

#22

Post by 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

Re: What Is Electricity? (2013)

#23

Post by lilgreenland »

esmi wrote: post #21
lilgreenland wrote: post #15

Earlier quoted context omitted.

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/

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…

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.

Re: What Is Electricity? (2013)

#24

Post by esmi »

lilgreenland wrote: post #23
esmi wrote: post #21

Earlier quoted context omitted.

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…

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.

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.

Re: What Is Electricity? (2013)

#25

Post by tntn »

geggam wrote: post #12

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 ?

They aren't "charged with" anything. Some elementary particles happen to interact with one another in a particular and consistent way, and we label them according to how they behave with something we call charge.

Electric charge is fundamental.

Re: What Is Electricity? (2013)

#26

Post by lilgreenland »

esmi wrote: post #24
lilgreenland wrote: post #23

Earlier quoted context omitted.

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.

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.

I see your point.

Re: What Is Electricity? (2013)

#27

Post by aivisol »

lilgreenland wrote: post #6

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...

Your notes are awesome. One thing I never thought of (and still have a doubt): can you really say that adding more resistance physically slows down the electrons? I mean, how slow can you make them move then by adding mega or giga ohm resistors? In metres per second? Isn't it more like that by adding more resistors there are less electrons which are able to pass it, which makes current flow less (not slower)? Just a random thought, without research.

Re: What Is Electricity? (2013)

#28

Post by sandworm101 »

aivisol wrote: post #27
lilgreenland wrote: post #6

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...

Your notes are awesome. One thing I never thought of (and still have a doubt): can you really say that adding more resistance physically slows down the electrons? I mean, how slow can you make them move then by adding mega or giga ohm resistors? In metres per second? Isn't it more like that by adding more resistors there are less electrons which are able to pass it, which makes current flow less (not slower)? Just a…

Electrons move at the same speed. In a low-resistance material (metal crystal) they move in an almost strait line. In a higher resitance material they take a longer path, and must line up (stop) to make it through bottlenecks. They only seem to be moving more slowly at a macroscopic level.

Re: What Is Electricity? (2013)

#29

Post by lilgreenland »

aivisol wrote: post #27
lilgreenland wrote: post #6

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...

Your notes are awesome. One thing I never thought of (and still have a doubt): can you really say that adding more resistance physically slows down the electrons? I mean, how slow can you make them move then by adding mega or giga ohm resistors? In metres per second? Isn't it more like that by adding more resistors there are less electrons which are able to pass it, which makes current flow less (not slower)? Just a…

I'm also speculating here, but I think resistance can manifest as slower electrons or as fewer electrons moving at the same speed.

On the wire, away from the resistors, the number of electrons that can move should stay constant, so the election drift velocity should drop as resistance increases.

https://en.wikipedia.org/wiki/Drift_velocity

https://codepen.io/lilgreenland/pen/xprGvr (not a mobile friendly link)

One more thing to add. Electron drift velocity isn't the same as signal propagation speed. Wires can transmit information at around 2/3 the speed of light, but the drift velocity of an electron in a wire is around walking speed.

Re: What Is Electricity? (2013)

#30

Post by aivisol »

lilgreenland wrote: post #29
aivisol wrote: post #27

Earlier quoted context omitted.

Your notes are awesome. One thing I never thought of (and still have a doubt): can you really say that adding more resistance physically slows down the electrons? I mean, how slow can you make them move then by adding mega or giga ohm resistors? In metres per second? Isn't it more like that by adding more resistors there are less electrons which are able to pass it, which makes current flow less (not slower)? Just a…

I'm also speculating here, but I think resistance can manifest as slower electrons or as fewer electrons moving at the same speed. On the wire, away from the resistors, the number of electrons that can move should stay constant, so the election drift velocity should drop as resistance increases. https://en.wikipedia.org/wiki/Drift_velocity https://codepen.io/lilgreenland/pen/xprGvr (not a mobile friendly link) One mo…

Thanks, point taken. And of course there are approximations and simplifications necessary when you try to explain this subject to high school students. I mean, that is the age when you still draw parallels from the physical world and it is easier to digest electron as a very small fast moving "ball" even though it is probably not.
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