Why we have - and + polarities in our homes wall outlets? I mean Its AC!?

Question

I know that in DC voltage we have - and + polarities. and in AC voltage we don't have any - or + polarities, because they will be changed by the hertz of the voltage per second. But if the outlets voltage is AC why it doesn't obey this rule?

(In AC voltage we don't have any - or + polarities, because they will be changed by the hertz of the voltage per second. But if the outlets voltage is AC why it doesn't obey this rule?)
Do we have two kind AC voltage?

Answer 1

Polarized AC plugs are not polarized for "+" and "-", they are polarized for "hot" and "neutral"

The neutral side (larger prong) is connected to earth ground, and to the center-tap of the distribution transformer (which is connected to earth ground). The 'hot' side of the polarized plug (the smaller prong) is connected to 120 VAC (either side of the distribution transformer).

By polarizing the plugs, this ensures that appliances which are not double-insulate have their chassis metal attached to earth-ground for safety, so you you won't get electrocuted.

Double-insulated appliances have no polarized plugs, neither do most 3-pronged plugs.
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Answer 2

In DC(Direct Voltage ) we have two Polarities one ie Positive(+) and the other is Negative. in AC(alternating current) we have sine wave, which starts from Zero degrees to 180 Degrees and to 360 degrees. it forms crest and trough. Hertz is the unit of Frequency. number of cycles per second is a frequency.

Answer 3

Sorry guy, your theory has been taken already... they're suggested as uninterruptible means ingredients (UPS). they are able to seamlessly keep your computing device and different comparable electronics online with a battery backup until means is restored. For longer outages, maximum persons use an outdoors AC generator to means severe aspects (refrigerator, freezer, heating, in step with probability computing device/modem). additionally, your DC means retailers theory does no longer artwork logistically. Your modem and computing device do certainly have means supply cords that convert one hundred twenty VAC into some DC voltage. So, as a fashion to apply your particular DC retailers during an emergency, you may ought to unplug the contraptions from the conventional retailers, connect a definite DC-DC twine, and then plug the gadget into the emergency DC retailers. So, this may well be fairly the headache and might additionally advise downtime at the same time as you turn over; with the aid of assessment a united statesmight have not got any downtime. additionally you should parent in the extra complexity of putting in emergency DC retailers in a house (greater confusion for electricians and sources proprietors). ultimately, a gasoline-powered generator in the basement isn't the appropriate theory when you consider that inner combustion engines supply off carbon monoxide. human beings have died from utilising products which includes gasoline-powered rigidity washers in enclosed areas. if certainty be told, a rather consumer-friendly thank you to devote suicide is to depart your motor vehicle engine idle in an enclosed storage. So... I advise sticking with the status quo right here. AC retailers for all, and united statesdevices for people who want emergency backup means for their desktops (on your case to maintain your telephone provider besides). edit: Oops, you probably did point out which you realize that battery backups already exist. nevertheless, the factors that I and others have made nevertheless stand.

Answer 4

if you are in Canada, your home may have originally been built in an area that had DC as the mains supply. DC mains work perfectly good for lighting and heating and were used in a few small communities until about 1980.

Answer 5

tlbs101 is absolutely right