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Why is electricity so hard to understand? (1989)

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Re: Why is electricity so hard to understand? (1989)

#81

Post by tomkat0789 »

justifier wrote: post #35
notalaser wrote: post #16

I think more than half the time I spent earning my EE degree has been spent unlearning the intuitive (but wrong) things that I was liberally taught. I was fortunate enough to have an exceptional Physics teacher in high school, who managed to avoid a lot of the bullshit that less fortunate students were fed; sadly, I compensated that with some of my own (misguided) self-study. This experience also taught me to activel…

From the linked notes: I never really understood capacitors until I started trying to construct proper water-analogies for them. Then I discovered that my electronics and physics classes had sent me down a dead-end path with their garbage about "capacitors store electric charge." Since my discovery, I've gained significantly more expertise in circuit design, which leads me to a sad thought. Maybe the more skilled of…

+1 for drainpipe theory! As a ChemE grad student I took an EE control class after basically forgetting all the circuits knowledge I learned as an undergraduate (my high school didn't teach electronics and magnetism!). Water analogies were the only way I could do the problems with circuits. Drainpipe theory actually made me wonder what was ever so hard about that part of physics class...

Re: Why is electricity so hard to understand? (1989)

#82

Post by gohrt »

nilkn wrote: post #56
justifier wrote: post #35

Earlier quoted context omitted.

From the linked notes: I never really understood capacitors until I started trying to construct proper water-analogies for them. Then I discovered that my electronics and physics classes had sent me down a dead-end path with their garbage about "capacitors store electric charge." Since my discovery, I've gained significantly more expertise in circuit design, which leads me to a sad thought. Maybe the more skilled of…

I still remember struggling with fractions when I was young. The funny thing is that I ended up majoring in math in college (at a highly ranked one at that), and I did very well, even publishing research in differential topology as an undergrad. How can someone who struggled to even grok fractions end up being successful in pure mathematics? I think it's because all my teachers operated off the assumption that kids c…

You're pinning too much on supposed bad teachers, and not enough on your past-self's youthful incomplete understanding.

1/2 of a pie is 2/4 of a pie, 2 slices of four is the same fraction as 1 slice of 2. It's exactly the same idea as the equivalence classes, where the ratio matters but the description does not. You just didn't understand that at the time.

> the very idea of discussing solutions to an equation will never be allowed in an elementary school classroom.

My kid is in first grade and his homework is to solve equations of the form "7+2=__" and "9-__=7"

Re: Why is electricity so hard to understand? (1989)

#83

Post by gohrt »

mjevans wrote: post #73
Animats wrote: post #69

Earlier quoted context omitted.

A practical impact of this - tool users from metric countries don't think in fractions. The notion that the next larger wrench after 1/8 is 5/32 is alien to people brought up with the metric system. Metric bolt heads are integral numbers of millimeters.

The irrational part of this is that the 'wrench system' is actually sized in 32nds of an inch, and thus would be much easier to comprehend with 'improper fractions'. 4/32, 5/32, 6/32, 8/32 ... etc

Or just "size 4, size 5", etc, with the "/32" as overall metadata

Re: Why is electricity so hard to understand? (1989)

#84

Post by arve0 »

feedjoelpie wrote: post #44
overcast wrote: post #27

The real question is, why is this website so hard to understand? Publishing what looks like someones personal notebook isn't helping the cause here.

Poor selection of link. Fortunately the author saw us and pointed us toward the articles instead of the raw notes: http://amasci.com/miscon/whyhard1.html#def

This should be the top comment.

Re: Why is electricity so hard to understand? (1989)

#85

Post by nilkn »

gohrt wrote: post #82
nilkn wrote: post #56

Earlier quoted context omitted.

I still remember struggling with fractions when I was young. The funny thing is that I ended up majoring in math in college (at a highly ranked one at that), and I did very well, even publishing research in differential topology as an undergrad. How can someone who struggled to even grok fractions end up being successful in pure mathematics? I think it's because all my teachers operated off the assumption that kids c…

You're pinning too much on supposed bad teachers, and not enough on your past-self's youthful incomplete understanding. 1/2 of a pie is 2/4 of a pie, 2 slices of four is the same fraction as 1 slice of 2. It's exactly the same idea as the equivalence classes, where the ratio matters but the description does not. You just didn't understand that at the time. > the very idea of discussing solutions to an equation will n…

With all due respect, that sounds like straight-up circular logic to me. You're arguing that 1/2 = 2/4 because "1/2 [...] is [...] 2/4". You're just restating the conclusion as an explanation of itself, which is completely unsatisfactory.

Another way of putting it:

> 2 slices of four is the same fraction as 1 slice of 2.

The phrase "is the same fraction as" is obviously inappropriate and explicitly circular and self-referential in any definition of "fraction". I don't think you've thought about this as deeply as you think you have.

Re: Why is electricity so hard to understand? (1989)

#86

Post by bandrami »

notalaser wrote: post #16

I think more than half the time I spent earning my EE degree has been spent unlearning the intuitive (but wrong) things that I was liberally taught. I was fortunate enough to have an exceptional Physics teacher in high school, who managed to avoid a lot of the bullshit that less fortunate students were fed; sadly, I compensated that with some of my own (misguided) self-study. This experience also taught me to activel…

Intuitive but wrong (and doggedly persistent) idea #1: "electric current is moving electrons". It is moving photons, exciting (largely) stationary electrons. I can't stress how crucial overcoming that misconception was when I was doing EE.

Re: Why is electricity so hard to understand? (1989)

#87

Post by JadeNB »

tantalor wrote: post #72
JadeNB wrote: post #68

Earlier quoted context omitted.

> > But it gets even more confusing when they say "we credited your account" or "your account was debited". > From your business's perspective, your bank account is an asset, so when they deposit into it, then its value increases, hence "debit". But what you're describing (a business depositing money into your account) is not what I, as a non-business owner, understand by "your account was debited". Businesses with w…

For the "we debited your account" terminology to be correct, you must consider it from the perspective of the other party. For example, suppose you go into the bank and withdraw $10 and they charge a $1 fee. The transaction looks like this: * Credits: $1 (bank income), $10 (bank assets) * Debit: $11 (customer liability) So when you get your account statement, it will say "$11 debit", because from their perspective, i…

I know that this isn't the point of this thread, so I'll stop after asking one more question. (This may be a terminally wrong-headed question, and I apologise in advance if so.)

Despite your very clear explanation, I'm still confused by:

> > But it gets even more confusing when they say "we credited your account" or "your account was debited".

> From your business's perspective, your bank account is an asset, so when they deposit into it, then its value increases, hence "debit".

Is it correct that the 'you' of the first post, in "your account was debited" (me the non-business owner), is the 'they' in the second post, of "when they deposit into it" (written from the perspective of the business owner, so that 'you' is no longer me)?

Re: Why is electricity so hard to understand? (1989)

#88

Post by notalaser »

fzzzy wrote: post #48
notalaser wrote: post #43

Earlier quoted context omitted.

As far as circuits go, this is about the closest high school Physics gets to truth (and it's decently close, compared to how wrong it gets e.g. capacitors): > In high school they told me, no no, they don't move at the speed of light, just when one electron enters the conductor, another one on the other side will leave the conductor, like with peas in a straw. And this enter/leaf is at the speed of light. although "en…

> If they taught you that, they are most definitely wrong, it sounds loosely like induction, but with two strange names instead of "electric" and "magnetic" :-). I don't think "definitely wrong" is a good description. electrostatic and electrodynamic are perfectly good, if somewhat archaic, terms for the electric and magnetic fields. (E and H fields)

Ah. That's a terminology fuck-up on my side, then. I've never encountered this convention, but classical electromagnetism has almost two centuries of history behind it. A lot of weird names have been used for a lot of things.

For what it's worth, though, these are terrible names, archaic or not :-D. If they ever were in use, I'm glad we moved on.

Re: Why is electricity so hard to understand? (1989)

#89

Post by seanp2k2 »

justifier wrote: post #64
seiferteric wrote: post #49

Earlier quoted context omitted.

Not really sure I like that link. He seems to suggest that capacitors store "energy" instead of charge, which is just as ambiguous really. It's not like there is some sort of energy particle either. Of course what's really happening is that you are creating an electric potential between two plates. It's true that the net charge is the same, but you are moving electrons from one plate and forcing them (doing work) int…

i agree, I linked more for the similarity in experience between the gp and the author in regard their unlearning I prefer your clarifications when considering the function of capacitors That said, water does attract water.. the term used to describe the phenomena is cohesion https://en.m.wikipedia.org/wiki/Cohesion_(chemistry)

What if the iron sphere contained an osmotic membrane?

Re: Why is electricity so hard to understand? (1989)

#90

Post by justifier »

gohrt wrote: post #80
justifier wrote: post #64

Earlier quoted context omitted.

i agree, I linked more for the similarity in experience between the gp and the author in regard their unlearning I prefer your clarifications when considering the function of capacitors That said, water does attract water.. the term used to describe the phenomena is cohesion https://en.m.wikipedia.org/wiki/Cohesion_(chemistry)

Cohesion is not an inverse-square field

gp> because water does not attract other water in any way

though i was merely addressing this quote your comment confuses me both in fillip and content

from cohesion wiki(o):

Water, for example, is strongly cohesive as each molecule may make four hydrogen bonds to other water molecules in a tetrahedral configuration. This results in a relatively strong Coulomb force between molecules.

from coulomb force wiki(i):

Coulomb's law or Coulomb's inverse-square law, is a law of physics that describes force interacting between static electrically charged particles.

(o) https://en.wikipedia.org/wiki/Cohesion_(chemistry)

(i) https://en.wikipedia.org/wiki/Coulomb%27s_law

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