# Why are plugs polarized?



## Kumar (Aug 1, 2008)

If A/C, is alternating current.... why do they make all 2 prong plugs polarized? It never mattered in the past which way you had it plugged in, why does it matter now?


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## Bushytails (Aug 1, 2008)

In most countries, the neutral is considered to be at the same potential as ground, and thus more safe.  The classic example is a desk lamp.  The hot wire goes to the switch, then to the small bump at the back of the lamp socket, while the large threaded ring on the socket is wired to the neutral.  When you plug the lamp in, since the neutral is wired to the shell, even if you stick your hands in the lamp, you contact the safe neutral, not the dangerous hot.  And when you turn the switch off, it disconnects the hot, leaving the entire socket safe.  If you were able to plug the lamp in backwards, the outside of the socket would be hot, waiting to electrocute the first person to try changing the bulb - and as the switch would now be in the neutral wire, not the hot wire, the whole socket would still be live even when the light is switched off.

--Bushytails


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## kshaeta (Aug 17, 2009)

But, don't you generally have the wires attached to sections that you electrify, no?  usually, there are spots where I connect the wires to, and these points are generally insolated from the remainder of, in this case, the lamp.

So are you saying that I can touch the white wire, and everything is a-ok, because there is no current there? Hmm.....  the only one I know I can touch is the green one, or the bare one... because that grounds everything out.


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## speedy petey (Aug 23, 2009)

kshaeta said:


> So are you saying that I can touch the white wire, and everything is a-ok, because there is no current there? Hmm.....  the only one I know I can touch is the green one, or the bare one... because that grounds everything out.


No, you can technically touch the white because there is no voltage there. There IS current when a load is applied. Also, if there is a load applied, and the neutral opens ahead of the appliance then there WILL be voltage present by backfeeding through the load. 

Grounding and bonding can be VERY in depth and confusing, even to pros, so I will not get that deep into it here.

The reason for polarization is safety as Bushy stated. A load will work just fine if it is wired backwards, it will just not be safe, or legal.


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## rokhsmith (Jul 6, 2010)

My home  is connected to a 240 VAC two-phase mains supply, with two hot circuits and a neutral return. The two hot circuits are 120 VAC each and operate 180 degrees out of phase with one another, but I am getting a start getting prepared, and I don't know if they will need electrical adapters to plug in.


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