I want my electric changed from AC to DC

[RosemontCrest]

Welcome to my killfile, moron.

[Charlie]

Let me tell you. I grew up in a section of Boston that had DC until sometime in late 1940s. This was supplied by Boston Edison.

You don't ever be in that situation.

Charlie

[Jon Danniken]

Whatever you do, don't let him near any elephants!

Jon

[mkirsch1]

You can't get DC because the NIMBY crowd won't let the electric company put up a powerplant on every street corner!

Don't blame the power company. Blame your neighbors!

[Ivan]

Just in case this guy was serious:

1) What makes you think DC is cheaper if nobody offers it for sale? 2) Don't blame the people you spoke to on the phone for not knowing about DC--odds are you were the first person to make this request in the last 90 years--if ever. 3) I used to work in a NY office building with DC; since that wouldn't run air-conditioning, they gave us salt tablets. My college dorm was DC, too, and we had to buy converters to run our stereo and refrigerator--with the amount of electronics in today's dorms, we would have been driven crazy.

[J_Heffron]

Even though it's not practical to distribute DC because of the wire thickness needed as well as losses, in some ways I can see where there can be some confusion. With DC, the power goes directly to the device. For example, in a flashlight, the DC batteries send the electric power directly to the lightbulb (thus the word DIRECT).

With AC, the power goes thru the bulb and is returned to the source minus what was lost from heating the filament in the bulb (mostly the loss is from heat). Knowing that, I always wondered just how much of the electric is returned to the power company in an AC system. Since that returned power has gone thru our electric meter, does the power company sell the same electric twice or more times? Maybe there is some truth in DC being cheaper to the consumer, (not taking into consideration the much higher costs to distribute it). I have always wondered what happened to that returned power in an AC system.

As for safety, I have never experienced a 120volt DC shock. Has anyone? Is it less painful or harmful than 120v AC? I have no idea.... I know that a 12VDC car battery can not shock a person, or at least it's not noticable.

[Tony Hwang]

Hi, You sound so SIMPLISTIC! Think basic Ohm's law again and law of energy conservation. Power(energy) never gets lost for one.

[Peter]

The great danger from power company AC (more so in the Northern Hemisphere than in the rest of the world) is the 60 Hz frequency - which is close enough to your heart muscle's pacemaker to throw you into ventricular fibrillation (which is lethal unless defibrillated with a DC shock). Outside of the Northern Hemisphere they tend to use 50 Hz, which is somewhat less dangerous because it is less likely than 60 Hz to ruin your entire day!

AC shocks produce a sensation of intense vibration without a lot of motion in your muscles, which can make it very easy to continue to hold on to whatever you have touched that is conducting the shock. DC shocks produce a violent contraction in the muscles, which if you are lucky will cause you to jerk away from the conducting object. They both can be quite painful, depending upon the amount of current and the duration of the shocks.

Don't believe that you cannot receive a really painful and/or injurious shock from a car battery. It depends upon your resistance (are you full of perspiration at the time you receive the shock or is your skin entirely intact and dry). Car batteries can deliver a really nasty high amperage shock if the resistance in the shock path is low and you can get really nasty burns from the heat that can be generated.

The damage from a shock is related to the energy (watts) delivered which is the product of the voltage and the current. The lower the resistance, the higher the current (given a constant voltage).

[J_Heffron]

Interesting info..... I never knew that about the "pacemaker". Why do they use 50 or 60 Hz in different places? Who determined what they use, and why? I imagine that what ever is connected to it will operate differently too, except for filament lightbulbs. What effect does it have on a motor made for 60hz if its run on 50hz? Or a transformer? And what about a SCR light dimmer?

Come to think about it, what determines whether the output from a generator is 50 or 60 hz? Is it the number of windings in the generator coil, or the speed it spins, or what? What would happen if they used 30 hz, or 80? I understand how generators work, but I never understood how they achieve the HZ rate. I can only assume that the output from a portable gasoline generator in the USA is 60Hz, so it matches that of the common outlets in this part of the world. Most of the time when you buy a generator, you only look at the amps or watts rating, and whether they provide 120V or 240V (or both).

What comes from a car's ignition coil? I got knocked on my ass from that a few times. Damn that hurts !!!!

Guess I have been lucky. I never have felt a thing from touching a live 12v wire in a car.

[Existential Angst]

Tony, did you BUY your EE degree, thru the mail? The laws of thermo notwithstanding, USEFUL power (ie, high-quality low-entropy power) is ALWAYS lost/degraded. To, uhhh, heat.....

The OP (or Heffron) is in a sense right, in that the *electrons* are proly recycled, but they have to be re-energized. Ergo Ohm's Law ---> Voltage *drop*, in joules per coulomb of electrons.

AC is proly easier to produce from a generator pov, as DC requires a split commutator, which wears. And still, the DC is probably not constant, but more like rectified, ie, sinusoidal "humps", and would still need filtering, etc. Or so I believe....

The main advantage of AC is the step up/step down-ability with transformers. Ergo, the efficiency of hi-voltage lines over distance, low voltage in neighborhoods.

HOWEVER, I read recently that research into high-voltage transmission was suggesting that very high voltage DC transmission was more efficient that AC -- proly due to lack of capacitance/inductive effects et al, or some other wizardry -- and that with the advent of solid state inverters, transforming DC to AC would be less problematic, rendering DC transmission ultimately viable.

As far as which to use in the house, proly doesn't really matter. But, good luck running 99% of modern appliances/electronics off DC. Which, prior to inverters, would have been near-impossible for low-voltage circuits.

As to which is safer, AC certainly arcs less, and DC would seem to more readily polarize tissue, thus more readily rendering muscles catatonic, esp. the heart. I subscribe to this opinion. AC *can* do the same, from first-hand experience, but DC certainly does it better.

HOWEVER, I have read medical opinion to the opposite, that AC is the more dangerous, altho with no real physiologic reasoning. I suspect they are wrong.

Most electricians consider DC far more troublesome.

Along these lines,

seems to suggest that DC (or damped sinusoidal, or slow biphasic) is more effective and requires lower voltages to be effective. Which suggests that DC is indeed more physiologically potent.

True AC in defibrillation, esp. at 60 hz, is likely hit and miss, phase-wise. Whereas DC defibrillation would either be "all hit" or "all miss".... ergo the biphasic deal.

All in all, the OP is a troll -- and an idiot. Bob-tx's 4/4 post on electricity was far funnier.

NYC provided DC to various buildings, mostly for their elevator service, I believe. I think someone posted here that this may have been discontinued altogether, but in the 80's, you bumped into it every now and then.

Mebbe the OP can find one of these old buildings.....

And, with all due respect, J Heffron needs to read a book on applied electricity.... goodgawd.... Hey, Tony, mebbe you and Heffron can chip in on an electricity book -- mebbe one without calculus....

[krw]

Blame Congress. They forced AC on everyone else, but they use DC themselves.

[clare]

Boy - you want to learn about electricity and electrical theory. DC and AC work EXACTLY the same, except AC reverses irself 50 or 60 times a second. The power is ALL used in the load, either AC or DC.

The big problem with DC is switching it. On AC the current crosses zero twice in each cycle - so 100 or 120 times a second. This quenches the arc - in DC the current is constant and switchgear flashover is always a problem

As for safety - AC and DC are relatively equal as far as shocks are concerned - if 12 volts DC does not give a shock, 12 volts AC won't either. The only difference is a DC shock is a "single hit" while AC is a "buzzzz" WHich is more dangerous? Since AC hurts more, I'd say DC is the more dangerous - easier to ignore??????

[clare]

In excess of 60,000 volts AC

It takes an extremely unlikely set of circumstances to lower the resistance of the body enough to let a 12 volt battery pass much current through that body. Basically it will involve mucous membranes or extreme saturation.

12 volts AC will give you a "tingle" long before you will feel DC and you can get a tingle on your toungue from a half dead 9 volt battery

Actually it is strictly the CURRENT - but it takes voltage to push that current, and if the resistance is low enough that 2 volts can cause the lethal current to flow, 2 volts COULD kill you.

I'm not saying there is a likely scenario where 2 volts could cause that current to flow - it's all Ohm's Law.

If the resistance is high enough that it takes 90 volts to force a lethal current through the body, 50 volts might be painfull, but wouldn't kill.

[Charlie]

If you ever have the opportunity to go swimming and boating in the salt water of the ocean, climb out of the water and while nice and wet lay your arm across the terminals of the 12 vdc battery used for starting the engine. A different and unique experience!

[Jules Richardson]

Lots of old railroad engineers have told me that DC was far worse because it can make muscles contract - and then you can't let go of whatever it is that's causing the shock. Whether there's truth in that, I'm not sure...

I don't know how many 240V AC shocks I've had over the years when I lived in the UK, but certainly quite a few. I'm yet to get zapped by US power... :-)

cheers

Jules

[hallerb]

AC was adopted in the US because its easy to transport, stepping up and down voltages to send current cross country.

thomas edison prefered DC, thinking it was safer

[LSMFT]

Nothing is your house will run except incandescent lights. Freezer, Refrigerator, TV, stereo, appliances, tools, nothing will work on DC unless you change it all out with DC appliances. Build your own rectifier bridge and make your own DC. Solar panels put out DC, get some of those.

[notbob]

That's DC, not AC. It feels like AC cuz it's being delivered repeatedly, the faster the engine's RPMs --and thus the distributor-- the faster the repititions of coil dicharges (X4, X6. X8).

nb

[keith]

History.

The power companies, then the governments involved (to homogenize service).

Some yes, some no.

Correct, though there is some flicker from light bulbs, too.

Depends on the motor. An induction motor will run at the line frequency, in this case at 5/6ths the RPM. A universal motor won't care.

A 50Hz transformer will run at 60Hz just fine. A 60Hz transformer has to be derated to run at 50Hz or it'll get too hot.

Should work fine at either frequency.

Both the number of poles (not the number of turns) and the RPM.

Nights would flicker, there would be more loss.

KVA rating is rather important too.

Anything less that 50V is considered "safe" to touch. Your skin has a natural resistance that protects you. Penetrate the skin and all bets are off. Lay your tongue on a 9v battery and see what it tastes like. ;-)

nonsense.

[keith]

There is.

It hurts too, but our normal household service is half (120V) of what you have. A 240V outlet, only used for large appliances, has two such wires (the 240V is split with a center tap tied to ground) but you'd have to work to get across both wires.