What's the point of "polarized" outlets?

[yukichigai]

After taking Physics III last year I learned all about AC power, including the fact that the positive and negative contacts switch polarity 60 times a second. (At least here in the US anyway) Useful tidbit of information; explains why sticking a fork in an outlet didn't kill me as a kid. However it made me realize that my conception of why many appliances have polarized plugs is flawed. I always thought it was because the big plug was the positive and the smaller one was the negative. But that's not true. So here's my question: what's the point of making appliances with polarized plugs. Is it simply that the older, non-polarized outlets couldn't handle as much voltage/amperage/whatever as the new "polarized" standard, or what?

 

[MikeyIs4Dcats]

ask and ye shall receive!

http://www.newton.dep.anl.gov/askasci/eng99/eng99158.htm

 

[yukichigai]

Okay, so then the larger port is the ground, and the smaller one is the AC? Hrm, so what's the point of a ground wire then? Or am I missing something. Gahh, I'm no Electrical Engineer! My brain itches!

 

[MikeyIs4Dcats]

ground keeps you from being electricuted should the wiring short circuit.

 

[Brutuskend]

Originally posted by: yukichigai
Okay, so then the larger port is the ground, and the smaller one is the AC? Hrm, so what's the point of a ground wire then? Or am I missing something. Gahh, I'm no Electrical Engineer! My brain itches!

Get a nail gun and scratch it!

 

[Amorphus]

It took you until Physics 3 to get to AC power?

 

[rectifire]

The original point of the ground on an AC outlet is to provide a path to ground in case of electrical malfunction in the device.
If the device malfunctions and sends power out to a part that the user commonly touches, that power can and often does use the person as a path to ground (you get shocked). If however, there is a low resistance path to ground in that device, the power will be harmlessly shunted away to ground, thereby protecting the user.

In one word: SAFETY

It has only been in the last decade or two that the use of a ground conductor has become a necessity for the sake of sensitive electronics. Even so, the primary reason for the ground conductor on an AC outlet is and always will be for safety.

Please note that the unpowered side of the AC receptacle is called the "Neutral", not ground. Though the neutral is intentionally grounded and provides for a direct path to ground, it is always differentiated from the Ground conductor. This is because is is very possible to be shocked by the neutral conductor. If you interrupt the neutral and connect yourself in series, you WILL get shocked just as bad as if you held on to the hot wire and touched ground.

 

[Fiveohhh]

One of the points of the ground (if it hasn't been stated yet) is so if a hot wire breaks loose and touches the chassis, its going to blow a fuse rather than turning the chassis hot so when you touch it you ground it out. probably more reasons than that, but I know thats on of them

 

[So]

Originally posted by: MikeyIs4Dcats
ground keeps you from being electricuted should the wiring short circuit.

No, that's the direct to ground. The 'ground' side (i.e. minus still has a voltage on it, since everyone is dumping energy into that side). I'm just starting my EE courses though so I'm still not totally clear.

 

[yukichigai]

Originally posted by: Amorphus
It took you until Physics 3 to get to AC power?

It was more a matter that I didn't particularly care. I knew AC != DC, and that was all I really needed to know to get on with life. Once I took Physics I actually needed to learn it. (since it was on the test ) Like I said, I'm not an electrical engineer, so what do I care?

Okay, so the big port is the ground, the smaller one is "hot", and the bottom one is... another ground?

 

[Brutuskend]

I think it's more like juice in. juice out and ground.

Though I could be wrong.

 

[silverpig]

Polarized plugs exist so that the switch on the device is between the AC source and the load. That way, if you touch the load with the device plugged in, there's no chance of shock as it's only connected to ground.

If your toaster was unpolarized and you plugged it in backwards, had the toaster off, and jammed a knife in it, you'd get shocked.

AC----switch----elements----ground
Switch keeps elements isolated to ground

Reverse plug:

AC----elements----switch-----ground
You touch the element, you get a shock.

The polarized plug makes it so you can only plug it in the first way.

 

[yukichigai]

Ahh, k. I think I get it. Polarized port is the neutral or "cold", unpolarized is "hot" and the bottom one is the ground. K. That makes sense.

So beyond the whole "getting your happy ass shocked" bit there's no other reason for it? Groovy.

 

[silverpig]

Originally posted by: Brutuskend
I think it's more like juice in. juice out and ground.

Though I could be wrong.

Naw, that's for 220V. In a regular plug you have a hot wire and a neutral wire. In a 3-prong it's hot, neutral ground. For 220V you have hot, hot (180 out of phase), neutral(?), and ground.