Electrical gurus

[cuong-nutz]

I was thinking (yes dangerous to do) during my long drive to my mother's how is it that no matter the orientation of the plug of an appliance or electronics to socket it still works normal? I'm mostly referring to ones that just use the two prong plug. Can someone explain?

[Skippii]

Originally Posted by cuong-nutz

I was thinking (yes dangerous to do) during my long drive to my mother's how is it that no matter the orientation of the plug of an appliance or electronics to socket it still works normal? I'm mostly referring to ones that just use the two prong plug. Can someone explain?

Easy. Alternating Current alternates (obviously) so it goes back and forth--there is no direction.

[Skippii]

Furthermore, most electronic things usually run off DC, and have a bridge rectifier which converts AC to DC. The rectifier has two identical AC inputs, one DC + output, and one DC - output. So anything that does require correct polarity will get it, regardless of input.

[sombo]

To help simplify what skippii said for those don't speak electronics:

The electricity that comes out of your wall is called Alternating Current (or AC). The 3 parts of the plug are hot, ground, and neutral. With AC the power does not have a positive or negative (like you see on batteries) and flows in both directions.

Then you have what they call Direct Current (or DC). This is where you find the positive and negative. In DC, the power flows from positive to negative and all devices that run on it are very sensitive to this. In DC if you hook up the power backwards it will do harm to the circuit.

In most electronic devices you plug in to the wall, they either operate on AC or DC. Those that operate on AC can plug into the wall in either direction and it won't matter, these are usually simple things like motors or lights. Those that have the plugs that can only go in one way usually are more complex and operate on DC. What they do is take the AC coming out of the wall and convert it internally to DC in order to operate. I hope this helps.

[CynicalC]

Originally Posted by sombo

Those that have the plugs that can only go in one way usually are more complex and operate on DC.

Polarized plugs are standard now on any device with a switch. The reason it's polarized is to make sure the switch is on the hot leg. Otherwise all the components of the device would still be hot even if the switch was off. Generally not an issue unless you're doing something stupid like working inside a device that's still plugged it. But it's there to protect you.

So if you were to file down a polarized plug and plug it in backwards, the device would still work like normal. But when you turned it off, the components would still be hot.

[sombo]

Originally Posted by CynicalC

Polarized plugs are standard now on any device with a switch. The reason it's polarized is to make sure the switch is on the hot leg. Otherwise all the components of the device would still be hot even if the switch was off. Generally not an issue unless you're doing something stupid like working inside a device that's still plugged it. But it's there to protect you.

So if you were to file down a polarized plug and plug it in backwards, the device would still work like normal. But when you turned it off, the components would still be hot.

Not always. Like I said, most of the stuff that is polarized has a converter in it. Most stuff that doesn't have a convertor and runs on AC doesn't worry about polarization.

[CynicalC]

Yes always. Whether it has a converter in it is besides the point. Plugs are polarized so that the hot leg is switched and not the neutral. Obviously the device will work either way due to the nature of AC. But if the neutral leg is switched, the device is still hot and looking for ground. Whereas if the hot leg is switched, the device is neutral aka grounded.

[Apex]

Originally Posted by CynicalC

Yes always. Whether it has a converter in it is besides the point. Plugs are polarized so that the hot leg is switched and not the neutral. Obviously the device will work either way due to the nature of AC. But if the neutral leg is switched, the device is still hot and looking for ground. Whereas if the hot leg is switched, the device is neutral aka grounded.

This is true. 11 years of OSHA approved semi-conductor electrical safety classes will tell you the same. Polarization does matter.

To help them get around needing a ground, they must increase the insulation to an approved level and polarize the plugs to prevent electrocution. That is how they are deemed to be safe.

[Sailariel]

Mark, Having lived on a boat for 14 years, I got quite adept at DC wiring. When we bought our house in 04, my wife asked me to wire in an electrical outlet for her. Guess what--DC and AC are quite different. I connected two wires and got knocked clear across the room--literally blew me out of my shoes. Lesson Learned: That is exactly why God put electricians on earth

[Skippii]

To clarify something, when we say that AC has a hot and a neutral, we mean that neutral is 0 volts, and the hot lead changes from 169.7 volts, then down to -169.7 volts, then back up, 60 times per second. (169.7 is 120V times the square root of two). 169.7 volts of AC is equal in power to 120 volts of DC current through the same load.

Sometimes, with AC, though, BOTH leads are hot, even though they still use the same outlets as the Hot/neutral type. All kinds of electronic stuff will work just the same on this. This is called Balanced AC current. It is not very common, but it is used in places like recording studios where "clean" power is critical. In a circuit where both wires are hot, they are shifted 180 degrees out of phase with each other and each's peak voltage is reduced by half. This means that when one is at 0v, so is the other one, but when one peaks at 85v, the other one is at -85v.
The end result is that everything works exactly as it would with 120V standard AC...but you don't want to touch either wire even if it is switched off.

[cuong-nutz]

Thanks for the refresher everyone! I totally forgot about AC/DC and the band Like they say, you lose what you don't use often.

[HKr1]

Originally Posted by Skippii

To clarify something, when we say that AC has a hot and a neutral, we mean that neutral is 0 volts, and the hot lead changes from 169.7 volts, then down to -169.7 volts, then back up, 60 times per second. (169.7 is 120V times the square root of two). 169.7 volts of AC is equal in power to 120 volts of DC current through the same load.

Sometimes, with AC, though, BOTH leads are hot, even though they still use the same outlets as the Hot/neutral type. All kinds of electronic stuff will work just the same on this. This is called Balanced AC current. It is not very common, but it is used in places like recording studios where "clean" power is critical. In a circuit where both wires are hot, they are shifted 180 degrees out of phase with each other and each's peak voltage is reduced by half. This means that when one is at 0v, so is the other one, but when one peaks at 85v, the other one is at -85v.
The end result is that everything works exactly as it would with 120V standard AC...but you don't want to touch either wire even if it is switched off.

Thats the way it is on the ships. No neutral, both leads have 60v to get your 120v.

[Skippii]

I didn't know that about ships. Is that just because their power is inverted from batteries?

[HKr1]

Originally Posted by Skippii

I didn't know that about ships. Is that just because their power is inverted from batteries?

No earth ground. Generators are steam driven, or back up diesel. Really gets you trouble shooting a piece of gear. Fuse panel would be A, B & C... So if you lost a phase fuse, two pieces(or more) of gear would be running strange in series.

[Apex]

I don't miss working on a ship...