Future: DC yes, AC no?

Quote: Face

These are questions that keep me up at night. Seriously.

It's like a water hose. Voltage is the amount of
pressure, amps are the amount of water. Lots
of voltage and small amperage, like a stun gun,
means it won't hurt you. But a 12V battery can
pack a ton of amps sometimes that will knock
you on your ass.

In a stun gun you have a huge amount of pressure (volts)
delivering a tiny amount of current (amps) and
it JOLTS you because of the high voltage. Combine
high voltage with high amperage, like in a power
line, and you have the real thing.

Quote: Pacomartin

That's about 100 kwh per day. Nareed would go into shock if her usage passed 100 kWh in a day.

Nah.

I'd just look up sales of cardboard boxes and stake out a place under a bridge ;)

Quote: Nareed

Mostly atoms.

I laughed. Out loud and hard XD

Quote: Evenbob

It's like a water hose. Voltage is the amount of
pressure, amps are the amount of water. Lots
of voltage and small amperage, like a stun gun,
means it won't hurt you. But a 12V battery can
pack a ton of amps sometimes that will knock
you on your ass.

In a stun gun you have a huge amount of pressure (volts)
delivering a tiny amount of current (amps) and
it JOLTS you because of the high voltage. Combine
high voltage with high amperage, like in a power
line, and you have the real thing.

DAMMIT! I had worked out my own analogy and it was exactly a water hose I used. And the same idea about "pressure v volume". But I came to something that didn't fit and trashed the whole idea.

Thanks for getting me back on track. We're starting to get somewhere now...

Quote: Face

I laughed. Out loud and hard XD

Quantic scales are seriously weird. I assume loose electrons can stay loose for a while, before a hungry positive ion snaps them up. Then, too, in a copper wire, what happens isn't that electrons travel along it. Rather they go into copper atoms and kick loose electrons which were peaceably orbiting a nucleus, which then move to the next atom and do the same thing. Or so I gather.

Quote: Face

DAMMIT! I had worked out my own analogy and it was exactly a water hose I used.

It's an analogy that's been around since 1900.
The two work exactly the same way. All the
laws of electricity work out the same in a water
hose.

My bro in law is an electrical engineer for a major
local company. One thing he never does is touch
anything he works on with more than one hand.
He used to keep his left hand in his pocket, but
after 30 years it's just habit. The last thing you
want is current going thru your chest cavity by
using both hands at once. Still, he gets zapped
all the time, it goes with the job.

Quote: odiousgambit

Does everything in the house actually run on DC? I can only think of light bulbs at the moment that run right off of AC (no?), although I guess the number of things might surprise me. Plus maybe the various light bulbs run fine directly off DC.

But surely there are plenty of things operating on DC, now connected to AC, that would have to disable internal transformers to run directly off DC?

DC is better suited for those few items that need a little power available all the time. Motion sensing outdoor lights, cord-less phones and message machines, alarm system, clock-radio and a doorbell are good examples. Turning those appliances off at night and when the house is vacant to save power just defeats their purpose.

I don't know how many transformers are internal. I have pulled some out of "wood stoves" for examples. Electronics mostly use external transformers.

Emerge Alliance is promoting standards to use DC in commercial office buildings. I know of no such alliance for residential buildings. It's mostly people who are trying to live off the grid as much as possible.
http://www.emergealliance.org/About/OurMission.aspx

I know that the USB power standards that can deliver up to 100 Watts are considered the wave of the future.
http://www.usb.org/developers/powerdelivery/

Certainly a well designed modern home full of energy saving appliances should be able to run everything at 100W or less. But you would probably need a first rate HVAC system. Refrigerators can run on less than 100W.


12V DC televisions are at least 2-3 times as expensive as their AC counterparts with an external AC/DC transformer.
http://www.12volt-travel.com/12-volt-televisions-c-684.html

Another safety trick I learned was to test a wire with the back of your hand.

If the line was live, it would cause your hand to close, and you would grab air. Palm towards the wire, your muscles would contract and you might end up with a handful of wire and not be able to let go.

A hose and a river are good analogies for electricity.

Also, to move DC voltage around your house at levels that would be useful for electronic devices, 12V, 5V, 3.3V, or even less,
You would suffer from voltage drops from transmission losses over surprisingly short distances.

So again like it was mentioned before, you would need larger wires through the house, or higher voltages with switching transformers I.e power supplies at the outlets or right back into the devices again.

All devices would still need some internal regulation for their and a users safety.

So on the one hand I think HVDC looks like it works for long distance power transmission, I don't think households will be shifting from 120/240 vac anytime soon.

Quote: Dalex64

Another safety trick I learned was to test a wire with the back of your hand.

Probably better advice is to test with a cheap voltage tester, and then test with the back of your hand. That way you rule out most painful shocks, but you still avoid electrocution if you did something wrong.

Quote: Face

I laughed. Out loud and hard XD



DAMMIT! I had worked out my own analogy and it was exactly a water hose I used. And the same idea about "pressure v volume". But I came to something that didn't fit and trashed the whole idea.

Thanks for getting me back on track. We're starting to get somewhere now...

An extension to the hose analogy is that the size of the hose is ohms (the resistance of the electrical conductor). The more resistance you have the higher the pressure (voltage) you need to push a set flow of water (amps) throught the hose. We can also equate the volume of water that we collect at the end of the hose to the KWHR of electricity that you are charged for on you monthly bill.

The analogy does start to fall apart if you examine it to closely but it is an easy way to help visualize the magic that is electricity.

Quote: Pacomartin

Probably better advice is to test with a cheap voltage tester, and then test with the back of your hand. That way you rule out most painful shocks, but you still avoid electrocution if you did something wrong.

I didn't want to get too wordy, but I didn't mean that you should test for a live circuit with your hand, but rather as a last test to make sure it really was dead, and you sure would be surprised if it wasn't.

I've seen a few tradesman shortcuts, though. Shorting a circuit with a screwdriver so you didn't have to walk to the box or figure out what circuit it was - not good for the breaker!
Testing for gas leaks in a newly installed gas line with a lighter. Fine if you do it soon enough or the leak is as small as you would expect it to be if it were there, I guess.