BlueRaja - Danny Pflughoeft

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353 reputation
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bio website blueraja.com/blog
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visits member for 3 years, 8 months
seen 14 hours ago

Jul
9
comment How effective is speeding?
"it costs you an additional $1.50 an hour to go 5 mph over the speed limit" - That depends on the speed-limit... Also, cost-per-hour is a complete red-herring, what's important is cost-per-mile. No one goes out and drives for a specific time, they drive a specific distance. -1
Jun
17
comment Voltage and Current in transformers
I wrote a blog post about this a few years ago: blueraja.com/blog/194/do-transformers-obey-ohms-law
May
16
comment Integral equations contradict The Uncertainty Principle?
@Lucas Integrals are a mathematical tool, they're not inherently classical or quantum, and in fact are used extensively in both theories. So it's more like, in classical mechanics, integrals allow you to determine the position of a particle over time given its velocity-graph. They cannot be used in QM for that same purpose (due to the uncertainty principle), but they are used for many other calculations.
Apr
21
comment Birds sitting on electric wires: potential difference between their feet
This is only half the answer. The danger with the high-voltage "transmission" lines that span between cities is the current that would flow due to the bird's capacitance, not parallel-resistance. When the bird lands, its potential must equalize the power-line's, which for a 700kV line, could mean a large shock. It's basically a static-shock, but lasts longer due to the large capacitance of the power plant. It's a huge danger for electrical-line workers. To my knowledge, this shock should happen and could indeed kill a bird.
Feb
10
awarded  Custodian
Feb
10
reviewed Reject suggested edit on Why is gravitational potential energy negative, and what does that mean?
Feb
10
awarded  Popular Question
Nov
26
comment Some doubts about photons
This answer claims that light moves faster than the speed of light. That's very confusing.
Nov
20
comment Why don't metals bond when touched together?
There is a serious lack of videos about this on Youtube
Oct
31
comment Why does this perpetuum mobile not work?(Gases and Densities)
Is "perpetuum mobile" a common term for perpetual motion machine? I'd never heard of it before, and the wikipedia article is about music.
Oct
2
comment If I am travelling on a car at around 60 km/h, and I shine a light, does that mean that the light is travelling faster than the speed of light?
This is exactly the question Einstein asked, which led him to discover special relativity.
Sep
20
revised Does alternating current (AC) require a complete circuit?
Added a link
Sep
20
suggested suggested edit on Does alternating current (AC) require a complete circuit?
Sep
20
accepted Does alternating current (AC) require a complete circuit?
Sep
9
comment Are the air particles in today's wind on earth (more or less) the same as the air 2/3 billion years ago?
@user80551: It was a guesstimate. But even using, say, 10^18 molecules, pari/gp tells me there are still around 6800 $9$'s after the decimal.
Sep
9
comment Are the air particles in today's wind on earth (more or less) the same as the air 2/3 billion years ago?
"so the probability that a particular oxygen molecule hitting your face is [..] $\approx 1.58 \times 10^{-14}$, ie. basically 0" - Except that the number of molocules that hit your face in a second is somewhere on the order of $10^{23}$, which means that the probability that one of these atoms existed that long ago is $1-(1-1.58 \times 10^{-14})^{10^{23}} \approx 99.99999999999...\%$
Aug
29
awarded  Benefactor
Aug
29
revised Does alternating current (AC) require a complete circuit?
edited title
Aug
23
awarded  Nice Question
Aug
22
comment Does alternating current (AC) require a complete circuit?
udiboy: I don't think treating the two planets as separate plates of a single parallel-plate capacitor is a good abstraction for this problem. The issue is that, though the planets both have a very large charge capacity, the capacitance of that system would be almost 0. This is not something that's ever dealt with in normal electronics, so I don't think there's a common electrical symbol that represents this situation. Though, @Ruslan may be right that each planet could be treated as a separate, extremely large capacitor - I really don't know.