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Why is electricity so hard to understand? (1989)

amasci.com

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

#131

Post by mannykannot »

soneca wrote: post #38

It looks like interesting content, but I got a little confused by the writing style and general layout. A more succinct, clearly defined structure would help me a lot. Each topic could be clearer on what is wrong and how is the right way. It would help a lot just to start with a clear: "What is the right definition of the word electricity?". Then, maybe a "What is "electrical phenomena" and some examples". "Correct d…

It turns out that this is not a good link to be starting with: see https://news.ycombinator.com/item?id=12901346

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

#132

Post by mannykannot »

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

I am not sure that is a big improvement. I dipped in here, and what I found was mostly a repetitive litany of complaints.

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

#133

Post by gugagore »

CamperBob2 wrote: post #127
gugagore wrote: post #123

Earlier quoted context omitted.

I didn't agree with what you wrote and maybe I can explain why. Springs store inches. You measure displacement in inches. Spring constant is just the value that relates stored inches to available force. (You can swap roles of force and displacement if you wish, the point is the same. It sounds bad to say springs store force or displacement, to me.)

But inches are an abstract measurement of distance. Electrons are a thing. (Well, depending on who you ask... no one has ever seen one, and some people have claimed half-jokingly there's only one electron in the entire universe: https://en.wikipedia.org/wiki/One-electron_universe .)

What?? Okay then count by lengths of the spacing of carbon molecules in graphite, or Plank lengths, or whatever.

I don't see why your objection is on inches or otherwise any unit I chose for dimension of length.

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

#134

Post by gugagore »

strictfp wrote: post #108
ambrop7 wrote: post #91

Earlier quoted context omitted.

My water analogy for a capacitor is a piston with pipes attached to both ends, with a spring system that pushes the piston towards the center position. Is that not a mathematically correct equivalent? (in an idealized system with no water resistance/inertia and disregarding that the piston is of fixed length - not that real capacitors have zero resistence, inductance or can store infinite charge)

Or just a membrane between the two sides?

Yeah, but maybe it's trickier to relate the restoration force of a membrane with displacement of water.

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

#135

Post by glandium »

tropo wrote: post #109
gohrt wrote: post #82

Earlier quoted context omitted.

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…

Similar problem from a local school: "__ - 9 = 9" The teacher would accept 9 or 0 as an answer, not 18. A parent (with math degree even) who was volunteering pointed out that 18 is correct. The teacher ruled against this, arguing that 18 was unacceptable because math with 2-digit numbers hadn't been covered yet. This was at a "good" school, in a county full of nerds. Such logic. Poor kids... and people wonder why kid…

How do they justify 0 or 9 as an answer? 9 - 9 is not 9, neither is 0 - 9.

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

#136

Post by slavik81 »

Asooka wrote: post #97
anu7df wrote: post #71

Earlier quoted context omitted.

I am all for introducing things the correct way, but this example of yours just does not work for me. Fractions as equivalence classes? or as a solution to an equation. No. That might work for you. In fact I might even argue that it only works for you - the child idealization created by "current you". There are many things wrong with US education. But I do not think introducing fractions using concrete examples is on…

Children take a long time to realise that one half of pizza is the same as two quarters. In general you can give a child less pizza and as long as it's the same number of pieces, they can't tell the difference. The well-known experiment is with presenting two sets of pieces of chocolate, one with less chocolate but more pieces and most children say the one with more pieces has more chocolate.

I'm not sure I believe this. My experience with children is that they're almost always smarter than I expected.

I think I've found the Wikipedia article about the effect, and the criticisms section [1] matches my bias, in that it suggests the children are confused because they are thinking not just about the material presented to them, but also why they're being asked.

[1] https://en.wikipedia.org/wiki/Conservation_(psychology)#Crit...

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

#137

Post by somedangedname »

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…

I suspect that the top search result for "water analogies" was hugged to death because of this comment.

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

#139

Post by slavik81 »

msandford wrote: post #112
gohrt wrote: post #83

Earlier quoted context omitted.

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

Except that there are wrench sizes in the /64 range as well. https://www.google.com/search?q=13%2F64%20wrench

Rather than 4/32, 9/64, 5/32, you'd have 4, 4.5, 5. That actually seems even better.

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

#140

Post by javajosh »

ambrop7 wrote: post #91
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…

My water analogy for a capacitor is a piston with pipes attached to both ends, with a spring system that pushes the piston towards the center position. Is that not a mathematically correct equivalent? (in an idealized system with no water resistance/inertia and disregarding that the piston is of fixed length - not that real capacitors have zero resistence, inductance or can store infinite charge)

From an energetic standpoint, a capacitor is something that takes a trickle over a long time, and releases a flood over a short time. So it would be a water tower with a small input and a large gated output.
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