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Why DC current is not used in Homes? Answered

Why DC current is not used in Homes as it is more safer than AC current.



Best Answer 6 years ago

There are two important factors that determine the use of AC instead of DC:

1) Power: Power is defined by the voltage x current (V x I = W). This equation indicates that the higher the voltage, the lower the current, and that the lower the voltage, the greater the current, for the same power (consumption). If using a very high current, the thickness of larger diameter wire must, therefore more expensive. The transmission lines would be very expensive, so high voltages are used (thousands of volts) to transmit from the generating plants, with relatively thin wires.

2) Transformers: These work only with AC power (for induction), and are necessary to lower the voltage and current to raise the nominal levels used in homes.

Both factors are complementary, DC cables using low voltages, it would be too expensive (cable diameter should be large), as could not be used transformers.

In the case of using their own sources of energy such as solar, wind, chemistry, etc.. The use of AC would only be for reasons of standards, and this is solved by voltage inverters (DC to AC),

The reason we use AC current in our homes is because AC can travel longer distances over the electrical grid (sometimes called stepping up the current)and the current changes polarity by cycles. Although DC could be used, it would require more infrastructure to provide electricity to every home. Also the current in the neutral wire would have to return to the generating station. The use of AC over DC was settled during the War of Currents between the American entrepreneurs Thomas Alva Edison and George Westinghouse. Nikola Tesla was in favor of using AC and he disagreed with Edison about the use of DC current. Tesla resigned working for Edison and later worked for Westinghouse. AC current prevailed and that is why most homes use AC current today.

Edison did not stand a chance in the "War of Currents" Simply because to transmit his DCurrent to a city he was building Boost Stations every Ten miles along the way, because of the I x I x R power losses ( I squared R Losses) !!!

And Edison liked to electrocute helpless Elephants, horses and goats :-/

Stepping DOWN the current, stepping UP the voltage.

Ac current to dc current why changed in home director we use ac current

in a way, DC can be safer than AC: (why?)

Imagine yourself working on wiring for an AC system. You weren't wearing safety gears, didnt deactivate the main switch and you accidentally touched one of the terminals/bare wire. If it was the neutral, you'd be safe right? But if it was the hot wire...well at at least, you'll get "punched" and will numb for a while but of course it can get worse.

Now imagine working on a DC wiring while not wearing safety gears and with the switch on: you touched the only one of the terminals or bare wires, you feel no electricity.

This is because DC needs to complete the circuit. While AC will flow towards the ground.

That is Silly Dangerous Thinking !!! Because any DC is also grounded !

Think about subway trains and street trolleys when you stand on the negative rails..

What DC house would not be grounded to avoid a pulsing lightening strike to hunt for its own ground....

In ultra-large systems, AC is converted into HIGH VOLTAGE DC for transmission, and chopped up at the other end. This prevents energy loss by radiation and eddycurrent and dielectric losses too.

DC is considerable MORE dangerous than AC, because it can cause muscles to spasm, and make you grip a live conductor harder. AC will "release" you 50 x a second.....

Low voltage DC in the home would cause all sorts of issues with fire and line losses.


"DC is considerable MORE dangerous than AC, because it can cause muscles to spasm, and make you grip a live conductor harder. AC will "release" you 50 x a second....."

How about: Try it out yourself?

The short story: No, the time a muscle takes to contract or loosen up with the very tightenedup state you get with direct high current muscle stimulation, is much longer than 1/50th of a second.

Before your grip looses noticably, your muscles will contract again.

Both will cause your muscles to spasm, Muscles don't care if the direction of electrones is one way or the other. Muscles contract due to electric impulses or the lack thereoff, they don't really care about electron flow.

High current is dangereus, no mater if it is DC or AC.
Saying one is more dangereus than the other, is like saying being burned at a 9000 degree stake is more dangereus than being burned at a 8000degree one.

in a way, DC can be safer than AC: (why?)

Imagine yourself working on wiring for an AC system. You weren't wearing safety gears, didnt deactivate the main switch and you accidentally touched one of the terminals/bare wire. If it was the neutral, you'd be safe right? But if it was the hot wire...well at at least, you'll get "punched" and will numb for a while but of course it can get worse.

Now imagine working on a DC wiring while not wearing safety gears and with the switch on: you touched the only one of the terminals or bare wires, you feel no electricity.

This is because DC needs to complete the circuit. While AC will flow towards the ground.

Let's not forget as well the source of power generation - whether it's today or many years ago, the origin of electricity tends to be some source of water, whether steam or in liquid state, causing a rotary or reciprocal motion upon some mechanical device which ultimately spins a generator turbine (which to a first approximation is simply a large electic engine "run in reverse" such that mechanical energy is the input and electrical engergy is the output."

Combined with the fact that a fairly simple, reliable, non-exotic, readily mass produced generator can follow the design of an AC electric engine. Which is to say that with common magnets and a rotating shaft inducing a rising then falling current with each cycle of spin, the output from this will be Alrternating Current, unless it is rectified in to DC. (but then there's loss and heat, and why not couple the rady-made AC current with the proposed AC power distribution network ?).

In any event, a class I took freshman year at a college in Boston which is known for it's study of technology, had us investigating the source of common technology legacies - in other words, why are we stuck with what we've got, and how difficult to replace ? Interestingly, the natural AC current coupled with efficiencies in long distance transmission were a natural fit, and turbines & generators were constructed to have rotating stators / shafts at ~ 60Hz +/- So indeed the 60Hz was a target, not an absolute guarantee, but largely achieved. Maybe 1 or 2 % deviation. Today, this is still true- whether coal. nuclear, or hydro-electric dam based power all have in common a generator (turbine) spinning and outputing some frequency of AC current at very high amperage. It may be today that 60Hz is artificially achieved to conform to the standard, but the origins of this design go way back to the nature of the generators manufactured and installed by.... WESTINGHOUSE! yes.

AC is good for transmission purpose only due to it's cost effective transmission at higher or lower voltages through transformers.The main issue with AC is that it is more dangerous to life due to it's alternating nature and it's friendly behavior to ground and it tends to transmit a noisy environment in electromagnetic wave transmission.Today we are capable of producing our own power via Solar panels and batteries at 12 Volt DC.But due to it's lower voltage it should be used for this only not be used for transmission. After that a high frequency SMPS or Inverter should be used to convert it to 220 Volt DC.Hear a high frequency device will be much lighter and efficient also.This 220 Volt DC should be run on same 220 Volt AC wire in our houses.Motor should be of 220 DC instead of 220 Volt AC, AC motor are induction mostly and due to capacitor there is a lose of power.

A Great shift in technology has occurred over three years ago when this subject first came up.

There is now a reasoned approach for moving to a very high voltage DC transmission power lines.

The chief advantage of DC over AC is no induced power loss into the surrounding environment, and that results in major energy transmission line savings.

Exchanging current for high voltage is as true for DC as it is for AC.

New semiconductors and circuit techniques are finally able to invert DC to lower voltage AC without the huge power losses that made this approach totally impractical three years ago !

On safety,

I lean towards AC over DC because AC is interrupted 100 to 120 times a second.

While DC will act to maintain a damaging current with the exception of a plasma Arc that will expand and self extinguish due magnetic pressure


What do you think ?

Yes this is one more advantage of AC over DC for safety purpose.But in AC for 220 Volt there is peak voltage of 311 Volt and 220 Volt is it's. RMS value so for DC we have to choose only 220 Volt.Both are dangerous but DC is more dangerous due to it's continues nature.But in AC we can get electric shock even touching it's single wire(Live wire).Because neutral wire is connected to ground at supplying transformer.So there should be 220 Volt DC at home also and a circuit breaker to cut supply when touched both wire accidentally.Due to DC there will be noise free environment.

DC will come back with a bang, reasons being, literally every device today at home residually runs on DC. Lets take lighting, every CFL or an LED lamp truly works on DC. The incoming 230V AC is rectified and the resulting true DC (322V) is stored on a capacitor (called a bank capacitor), the entire CFL circuit then works on this DC voltage. If the incoming DC voltage from a solar panel is configured to give 300V DC, it can be connected to this bank capacitor to run any CFL lamp. The same is true for a LED lamp. All heaters, irons, toasters etc can run directly on DC or AC with no modifications required. Let's take a modern day TV of any type. The same rectification and a bank capacitor is seen within. A 300V DC if applied directly from any source (could be a solar generated DC), the TV should work with no issues at all. The only device which truly runs on AC are the motors, compressors within fridges and air-conditioning equipment. Here again with variable frequency drives (VFD) used in modern refrigerators and air-conditioners (sold as inverter fridges or inverter air-conditioners), the tank capacitor within the VFD can take the 300V DC. So today, it is very much viable to have a truly DC home with every device within working on 300V DC. With distributed power generation with alternate sources of energy like Solar and Wind power, it is the right time to go for DC. Now regarding DC being more dangerous than AC, let me state here that both are equally dangerous and hence protection and safety concerns are equal. With my personal experience, DC is much safer and not as lethal as AC. I have frequently demonstrated (do not try it) DC versus AC supply at 110 Volts and let me state here that even at 110 Volts AC is lethal while DC is considerably safe. There are quite a number of videos on Youtube. I am working on a all DC project where every equipment one has in a typical household runs on 300V DC. There are some teething issues namely the switches, isolators etc, but these are all solvable as we work along. DC is coming back with a vengeance and am sure Edison for one will be turning in his grave after 100 plus years of resting.

sir am student of 4th b.tech ,I have much interest to work on dc.but I have no one to support

contact me through my email naikmm@gmail.com

DC is making a comeback in homes using solar cells and wind power. Some of those solar-powered homes use 12 volts and power things directly rather than converting up to 120 volts to power many items. There are many appliances that are made for camping and RV'ing that work on 12 volts so it makes sense to use DC.

i agree.battery. think about ur car. u have everything u need, today is positive, teck no,they have the answers..use 2 b ,like the old cars where u had the spark restorator 2 control the the amount of amps {load} high 2 start the car, low 2 run. same 2 apply 2 home. i don't know of any cars to day that has #12 r lower wire size, execpt from battery 2 starter..ur solor panels run the altanator with battery backup.

My experience with DC power: I am a telecommunications engineer building central offices for some of the largest telcos in the world. In other words, I know what I'm talking about. Everything we have runs on DC. We don't do AC. I manage multiple DC plants with well over a thousand AMPs worth of juice.

DC power is not more dangerous than AC. Quite to the contrary, if handled correctly it is much safer. We have what we call breaker distribution frames. This is where multiple DC feeds terminate into what really is the equivalent of a "DC breaker box" in a rack if you think of the AC world. It's 7' tall and loaded with breakers. You can reach into the back of those, grab the copper bus bars and if you are not wearing metal, come out without injury.

On a AC breaker box this could easily end in death. Don't do it. I have seen people on accident take a hot DC lead and contact metal with it and not be injured. With AC that person most likely would have got knocked across the room. The one true thing about DC is you will have much larger cables. The longer the distance, the larger the cable (or the greater the number of circular mills as we like to call it). But we also run the voltage at -51.4 volts.

There are some very vague generalizations that people are making here that are incorrect. Please keep comments on safety accurate or don't comment. People feel like they have to know everything and just because a person does a quick google to pretend they know doesn't mean they do. I only joined to respond to this because there is misinformation being stated as fact here.

One correction on my prior post. Our rectifiers that convert AC to DC I guess run on AC. Thats it. Nothing else does. One other huge advantage to DC power is the amount of cooling required for DC is far less than that of AC. And Tesla himself was in fact trying to run DC to the home. The worst thing I have ever encountered in a DC power configuration: thermal runaway. But this is more due to the float voltage of the DC plant not being set correctly or not being checked over time to ensure it is still correct, which in turn overcharges the battery strings (we have batteries for everything) and explosive gas is released. But you could argue that is not really related to DC itself and I would agree. Thats more human error.

If you ever intend to run on a solar power configuration you will need to understand DC power and theory. Or it will be to your advantage to as the configuration for solar powered homes does use DC power. So if you want out of the AC rat race, go to solar when it becomes more cost effective.


90% of my things run on DC current,
xbox, ps3, phones, TV(lcd etc), printers, everything I can see

Energy bulbs (these can run on dc or ac see youtube) /
LED household bulbs run on dc

i go into my kitchen and i think the toaster, kettle, microwave and fridge are all maybe 240vac

1) So why is the electric inside my home AC?
2) im not saying use 12VDC everywhere that would be ludicrous, but why is it not DC?
3) my xbox uses 12VDC and 5VDC same as my computer so obviously it can manage the change in voltage?
4) Could they not, with todays breakthroughs EITHER;
4a) Use High voltage DC to travel efficiently?
4b) or use the High voltage AC to travel, but when it reaches my home (or residential area) convert to 240VDC (or some ?VDC) instead of 240VAC

Then according to this really good youtube video ....


There would be less loss,
Less heat coming from the laptop or the back of the TV....

and OMG maybe no more Red Ring Of Death on the xbox

(oops i forgot MS are scared you will not buy another, so the multi-billion dollar/pound company, that's been making processors and such things for a very long time and getting it right, seem to make an xbox that always goes wrong!!) Slightly off topic :-P

life must be tough for you

I remember that Tramcars in Calcutta used to run on DC.
Does Electric Train run on DC? Or Diesel Train Engines run on DC as it has its own Generators.
It seems that Heavy Machinery run on DC.

The speed of an AC motor is closely tied to the AC frequency, hence they are very poor for variable-speed like trams/trains.
There are modern trains that do use AC motors (because they are more efficient), they use big-silicon to produce the output AC via DC, from probably 25KV AC.


No, it's not.
This is what Edison used to say about the Westinghouse system.



6 years ago

Just to add to what everybody else has said, -- DC works for transmitting data, both analog and digital. That is why your phone lines are DC. But AC works for transmitting power more efficiently. I think the reason for much of the home power stuff being 12 volt DC is that it is somewhat safer, BUT only AS 12 Volt. But you need a lot heavier cables to handle high amperage with 12 volt and thick copper wire is expensive. Its a lot cheaper and more efficient to use less wire with more insulation. I helped to set up a little wind generator and we had to pay a lot for the heavy cable that was needed, way more than it would have been for just regular house wire. The fact is they probably should be making those with 120 volt outputs, except that when you couple them up to storage batteries the batteries are all 12 volt based. What is really missing in this beginning industry is a set of standards that everybody will go with. Then the cost of all the stuff will come down and putting it all together to work correctly will become much simpler.
And yes, as the others brought out DC starts a lot more fires because people don't realize they need really heavy gauge cables to handle the amperage.


6 years ago

I don't know what makes you think DC is safer than AC; at normal household currents, either one will kill or injure just as easily as the other.
The myth that DC is safer than AC began when Thomas Edison (the patent holder for DC power generation systems) was attempting to discredit Westinghouse's AC system from being adopted as the model for municipal electric power.

IIRC, the myth was debunked using the electric chair - convicts had a far greater chance of surviving electrocution by AC than DC.

Of course, I may just be recalling another myth...

It is very difficult for me to select the best answer because again I am hearing that DC is going to come back in Homes.

Dipankar, when I was very young (4 years old), 1949) in my village was an old DC power plant, 220 volts. It was very noticeable the voltage drop proportional to the distance to the plant. Nearby, lights bright normally, but at 6 or 7 blocks were dim. The motors was often burned as a result.

Its only "coming back" for very, very special, off grid applications. Like I said, you won't see it used in general because using AC is much more sensible, and safer.

Power = current x voltage, but wasted energy = current^2 x resistance - so the higher the voltage, the less you waste in your wires - or the lower the chance of a fire.

In the USA for example, electrical fires are MUCH more common, because they use 110V supplies than in the rest of the 220V using world - for a given power, we need 1/2 the current.

If we used 12V supplies routinely - AC or DC, I hate to think what the fire stats would look like.


I remember when I was about 9 years old, we had DC in our homes and then around the year 1955 they started converting the home current to AC. I think at that time Calcutta City had its own Generating Unit. That is why I was curious to know when we had DC in our home why was it converted to AC.

I've read about this over the years.  The numbers may be off, I'm just going from memory but the point if valid.

DC is hard to step down without losses.  With AC you can use transformers.  When you generate DC you can only transmit it 20 to 30 miles before the resistance of the wire starts to degrade it too much.  You start out with 120 volts and at the end you only have 70 or 80.  With AC you start out with 15,000 and even after several hundred miles you still have 14,500 volts.  Using transformers along the way you convert the high voltage to 120 volts ac.  so you can build generating stations far apart rather than every 50 miles or so.

In the beginning there wasn't an easy way to convert dc to ac as there is now.  So the losses would be much more than they are today.

DC current is as dangerous as AC.  There are some situations where ac may cause more damage but you can die from getting your self across a battery such as from a Prius (700 volts).

DC also tends to generate A LOT more heat. When DC was being used fires were common, and power lines would fall frequently. That's actually where the then, Brooklyn Dodgers got their name, dodging falling or fallen power lines. Even Edison admitted before he died, that Tesla was right, and AC was the way to go.

No, I'm sorry. The Brooklyn Dodgers derived their name from "Trolley Dodgers":

New Yorkers ... routinely called anyone from Brooklyn a "trolley dodger", due to the vast network of street car lines criss-crossing the borough as people dodged trains to cross the streets.

(see Wikipedia, and the primary source citations therein).

DC is no safer than AC. The problem is that most real devices need a substantial amount of power, and both current and voltage (the product of which is power) can be fatal.

As has already been noted, the electrical distribution grid needs to be consistent. Since Edison lost the war with Westinghouse, the grid is AC, not DC.

Transformers only work with AC, so it's easier to use AC in the whole power grid.