Cool. 
I had a client that was a power company that had a “pumped storage facility” next to its nuclear plant. Essentially it was a hydro generator that could be run backwards, so that in addition to letting water run down from the reservoir through the turbine to generate electricity, you could power the turbine from outside electricity to pump water up into the reservoir. Later the water pumped up could be run back through the turbine to generate more electricity.
Although this was obviously an inefficient use of electricity, it was economically efficient, particularly in the summer when the demand for electricity during the day was very high for air conditioning, and thus daytime power could be sold for a high price. Because the nuclear plant would essentially run at full power continuously, at night when electric sale prices were the cheapest they had more power than they really needed. They could use this cheap power to run the pump and store the water overnight. Later, when the rates were higher during the day, they could run the hydro generator and sell the power at the premium daytime rate. Even though the process was electrically inefficient, using the cheap nighttime power to store water to be used to generate higher priced power later was a good deal for the company.
How much water did they pump? How many users did they serve?
And will do you wrong if you use your finger to lengthen a short circuit. :eek:
That makes no sense. A short circuit is, well, a short. Two conductors in contact that should not be. Sticking a paper clip into the business end of a plugged in extension cord for example.
I used to have one like that in Ensenada in the 70s. But it would stay on (continue to broadcast radio) for about 3 seconds after turning it off, and then continue to put out a quickly fading static sound for another 2 or 3 seconds after that. I figured it had a capacitor in it. Didn’t matter if we turned it off or unplugged it. I don’t remember if it was Thai manufacture
If you think shorting out a cap will get rid of all of the stored energy, think again. You’ve only eliminated the charge stored on the “plates”. Energy still remains, however, as a result of the polarization of the insulator (i. e., the “dielectric”). This is called dielectric absorption (DA). The amount depends on the material, but DA is far slower to build up and down, relative to the regular charging/discharging of a capacitor.
Where this really becomes a problem, is the high-voltage capacitors used in CRT televisions. You can short out cap for a minute, and come back an hour later and get a nasty spark (or a jolt to the hand as I can personally attest to). Some manufacturers used bleed resistors which involves putting a high resistance across a capacitor to ensure a continuous discharge path after voltage is removed, thus bleeding out the stored charge, along with the DA charge.
I think Teflon dielectric base caps have the lowest DA. I used one for a precision frequency oscillator years ago, but it was something like $80.00 for one capacitor (0.47 µF) and much, much larger than caps made of more conventional dielectrics.
As an aside, why are capacitances so often 47 times a power of ten? Why 0.47 µF instead of 0.5 µF?
It has to do with creating a sensible distribution of values. the standard E6 series does this by using the following base values: 10, 15, 22, 33, 47 and 68 and multiply or dividing by powers of 10. You’ll notice that the step between values gets larger as you follow the sequence–if you look closely, you’ll see a logical pattern. There is also an E3 series which uses 10, 22 and 47.
Resistors have those values, too and I never noticed it. :smack:
Yep. So do inductors. I wonder if discreet memristors will, as well?
It seems all of you posting have no knowledge of this subject at all and are guessing. Alternating Current (AC) power supplies are affected by capacitive and inductive load because the load type causes either the voltage or the current to lag behind the other by up to 90 degrees. For example, flourescent lights are capacitive loads, so a ballast transformer is fitted to each light to provide an inductive load to bring them into phase, otherwise other appliances in the vicinity could be affected as well. Most AC motors are required to have some capacitance loading in the circuit too. In extreme cases power meters have been known to go backwards under large out-of-phase loads! Most appliances are supplied via transformers (inductive loads) so the voltage is out of phase and lagging behind the current being drawn.
Speaking of having no knowledge and just guessing… No, my Down Under friend, this is completely, entirely and utterly incorrect. The magnetic ballast is an inductor, not a transformer, and is wired in series with the tube. When the tube is ignited, the gas inside is ionized. If there is nothing to limit the current, this ionized gas presents a very low resistance and the current rises rapidly. This is nothing like capacitance. In any case, since inductors react to rapid current changes by inducing a voltage in opposition to it, it serves to limit the current through the tube. Power factor and phase shifts have nothing, nada, zip to do with it.
My qualifications? I work at an engineering company which designs and builds three-phase power-quality equipment for computer data centers. I work with power factor on a daily basis. You’re welcome.
Exactly what in this thread have I posted is wrong or something I “guessed” at?
[Foghorn Leghorn] That’s a joke, son. [/Foghorn Leghorn]
Okay, per Una and Cecil’s instructions, I’ve unplugged everything in my house. I spend much of my time on the house’s lower level. Am I in any danger from electricity leaking out of the unused sockets and pooling down here?
And if you don’t make THAT reference you have no business being a Doper. 
Ah, gotcha. Evenly spaced in log space, and then rounded to two significant figures.
And why is that? Does it provide for creating different values in series or parallel, or for frequency calculations with resistors and caps?
You imply that the power company charges for watts used, even in reactive loads. The purveyors of power factor correction devices claim that they charge for volt-amps, which will be significantly higher than the watts in a highly reactive load, such as the motor of an air conditioner. They sell a capacitive device intended to bring the power factor back to near unity.
My reason for not trying one is that they had no provision for varying the capacitance, even for varying load conditions (one size fits all). So if it overcompensated and resulted in phase shift too capacitive, that would waste electricity when the inductance was lower than the nominal design value.
Question: DO the electric meters measure and charge you for actual watts used, or for volt-amps?? I asked the local power company and failed to get a clear answer.
Well, for openers, they charge by watt-hours, not watts, though large businesses may also have to pay a peak-watts charge.
My bill unequivocally charges by watt-hours, rather than volt-amp-hours. That does not preclude the possibility that meter watt-hours may actually be volt-amp-hours, uncorrected for power factor, and, according to Wikipedia, that possibility is the actual case.
Okay, three things made me wonder about Cecil’s column. The first is
, and Slug draws a guy pulling the plugs (by the cable, which I thought you shouldn’t do, but that’s another topic) from the power strip. Question: Don’t you American guys have access to power strips with switches? I have two - one for my TV, DVD player etc., and one for PC with monitor, loudspeakers etc. I turn both of the switches off when I’m finished with the appliances, one flick of the switch instead of pulling out several plugs.
Second, while measuring to get facts is certainly far better than guesstimating, I don’t know how
Cecil can extrapolate from one house - that’s not what I would call statistically relevant or typical.
Third, I don’t follow or share the logic/attitude that Cecil presents with
, esp. since one line earlier he admits
. I consider it a logical fallacy to look only at the big picture and therefore dismiss the little effects that add up. I don’t know the current numbers for the wasted energy in regard to standby/not properly shut off (often the case with newer appliances - even when you hit the power button, they still draw energy, not because of remote, but because the producers don’t power them off properly), but for comparison: if every normal light bulb in Germany were exchanged for an energy-saving bulb, we could shut off a whole damn nuclear power plant from the saved energy. So because small amounts add up in a large population, they’re also worth doing. (Of course, doing only the small things like changing light bulbs while ignoring the big issues like house-insulation or car emissions is the wrong way to save the planet). But I don’t understand why it has to be ** either/or instead of and** - I turn my appliances off (except for my VoIP telefone and answering machine) in the evening/morning, and then I take the subway to work.