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Comment Re: Tesla Is Good For All (Score 4, Insightful) 356

And that has been Tesla's argument for the last ten years, yet they still lose about $9,000 on each car they make.

"On" each car, or "for" each car?

"On" makes it sound like their marginal costs are negative -- that, literally, producing one more car increases their losses by $9K. Were it "for" each car, then they're losing money only after fixed costs, R&D, etc. are taken into account.

That latter makes considerably more sense -- folks can legitimately decide to back a company investing in itself rather than taking out a profit; indeed, Amazon has done that for years.

Comment Re:Heart valves? Refrigerators? Pah! (Score 3, Interesting) 65

please enlighten us as to why the fountain pin and/or feathered quill is superior to the free pens I get from the bank?

Y'know, I actually don't mind giving this a serious answer.

You don't need pressure to write with a fountain pen -- at all. (The modern competitor is a rollerball, not a ballpoint; rollerballs don't give you amount of flexibility on nib grind or opportunities for flex and shading effects that you get with a fountain, but at least you're not forced to use tons of pressure). Allows different, more comfortable grips.

Also, they're refillable with water-based inks -- meaning that they're not disposable, and that you have a huge amount of choice in terms of color and properties of your ink. Want an ink that's still viscous in below-freezing weather? I've got a bottle on my desk! Want an ink that changes from yellow to red depending on how much you're putting down on the paper? That too! Want an ink that responds to ultraviolet and is completely waterproof you can mix in with other inks that are water-soluable, so you can see where writing that's been washed away used to be under a blacklight?

Lots of room for geekery. :)

Comment Re:Yes more reliable (Score 1) 101

The idea is that your device runs a calendar app and syncs with Google Calendar. You then get notifications regardless if you are online or outside a coverage area,

And through what magic does that sync occur if you are offline or outside a coverage area?

I'm not foolisbn enough to give an advertizing company my callendar, but I'm pretty sure that Google Clendar uses TCP/IP to sync. Which means you have to have data reception. Which is much less avaiable than SMS.

Comment Re:Tesla enables Edison to win the endgame? (Score 1) 597

I said as much above.

In an AC system, that current is continuously changing, so those transmission lines are continuously radiating away some amount energy. But that's not all. If there are any conductors nearby, those E-M waves can induce a current in those conductors, and the resulting E-M waves from that induced current can drag on the AC line further. This mutual induction is how transformers work. But, along an AC transmission line, unwanted coupling results in transmission losses. So, an AC system has a built in, inherent source of losses in the alternating current itself.

...and...

In a DC system, with a fixed, perfectly resistive load, the current doesn't change, so there's no radiative losses. In the real world, though, the loading on the system is continually changing, so the actual current demand on the DC system will vary over time, and some energy will be radiated away. To some extent that can be filtered, but that's limited by the amount of storage you can put near the ends of the transmission.

Comment Re:Availability (Score 1) 692

Because it's cheaper to have an immortal serf class than it is to have to train up larval serfs for 20 years at a net negative value before they're useful? Young people are generally a resource sink with no return on investment for a couple decades.

Historically speaking, a young person began to earn an income much earlier than age 20. It's only our modern laws and policies that have been pushing this later and later. Even today this continues as more and more young people start their careers laden with high college debt.

Comment Re:capacitance loss (Score 1) 597

Capacitors store energy, they don't dissipate it. Likewise with inductors.

Transmission lines represent both capacitive and inductive loads simultaneously. The capacitance, inductance, resistance of the transmission line together combine to form the characteristic impedance of the line. (Ok, there's one additional term: the conductance of the dielectric between the conductors. But, for high voltage transmission lines that are widely separated, this term is effectively 0.)

The characteristic impedance of a transmission line is of primary importance for determining the ideal load impedance for the line. In an impedance matched system, the maximum power will be transmitted to the load with no reflections.

Reflections can cause a phase shift between voltage and current, making a transmission line effectively look reactive or inductive. (See surge impedance loading.) This can be corrected for in the same ways as reactive or inductive loads by adding capacitance or inductance elsewhere.

If the load itself is reactive or inductive then you can get reactive power transfer. Reactive vs. inductive is in some sense a matter of sign; in one, current leads voltage, in the other current lags voltage. In both cases, current is out of phase with voltage and that's the problem to be solved.

Reactive power doesn't transmit any actual power to the load, but it still sends current through the system. Current is subject to ohmic losses (thanks to our friend I*I*R). Sending current without delivering real power subjects you to losses without any benefits.

In general, the capacitance of the transmission line itself isn't the culprit on its own. Rather, if you have a reactive load (either capacitive or inductive), or you have imperfect impedance matching between the load and the transmission line, you can get current flowing through your wires that isn't driving a load. That excess current incurs plain ol' resistive losses.

There is one way high capacitance can cause real problems for transmission line management, though. The rate of propagation of waves through a conductor slows in proportion to the square root of the product of the inductance and the capacitance. So, for a highly capacitive line, reflections move slowly through the system, and it becomes more difficult to compensate for transients. That seems to be the real bugbear for buried high-capacitance lines. Again, you're not losing to the capacitance directly, but rather to the knock on effects that lead to poorly compensated reflections and reactive power transfer in the system.

(Dr. Jetton, if you're reading this... EE305 may have been 20 years ago for me, but I haven't completely forgotten it. And Dr. Schertz... I didn't completely forget my T-line theory either. I wouldn't be surprised if either of you would point out flaws in my summary above.)

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