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# Quick AC question

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I'm sorry I have to ask such a dumb question but every othere resourse is eplaining how to uses caps and resistors in AC and can't (to a full extent) answer my question.
I can't figure out what AC is.  I know what it stands for and that it goes at 60Hz.  I used to think there was a positive and a negative and the positive turned on and off at 60Hz but after learning about bridge rectifiers and seeing many otherr things I pretty sure its the polarity reversing itself at 60Hz.  (AS in lead 1 is + and lead 2 is - then lead 1 is - and lead 2 is + and so on)  Is this right?  I almost always am working with DC circuits but I stumbledd along a problem while wiring some outlets in a PSU.  I have 2 (light) switches and 2 outlets and I want to control the oulets with the the switches.  What I've done so far is wire the 2 black wire screws (on the 2 outlets) together (which is my mistake i think) and wired the white wires through the switches.  Then the mains that comes from the wall goes to the 2 outlets black wire and to the 2 switches.  In a DC circuit this would be fine but i think  I have it wrong...Maybe...if the power is being supplied to both black wires half the time but it has nowhere to ground because the white wire switch is off then I'd be ok for eing able to switch it right?
Thanks guys--if this is too confusing due to my wording I could make up a quick schematic for you if you like.

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Hi Um...Me,
In your 120VAC/60Hz system, black is the live wire and white is the neutral which is grounded at the power source. You should switch the black live wire and connect together the white wires because then when a switch is off its receptacle is dead. The way you have it, the receptacle is always live and waiting for the switch or your finger to complete the circuit.

AC is alternating current that can have its voltage changed easily with a transformer. The voltage and current change polarities gradually in a sine wave from positive down through 0V and down to negative then back up again over and over. The repetition rate is 60Hz.

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Well i have a wall plug that I bought--how do I know which is the hot wire?

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If it plugs-in both directions then you should use a double-pole switch to make certain that the live wire is switched.

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Where do you live?
Is it a three pin plug?

Here in the UK the live/phase/hot is brown, it's the left pin if you look at the plug with the pins facing you, you can easilly identify it when you open up the plug because it's the pin with the fuse connected to it.

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I live in the US and the cord I bought has just 2 plugs--the left on is bigger and I think is the neutral.  Anyone know this for sure?  The other end is just bare wire but I can just follow the side of the wire down to the end.

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I live in the US and the cord I bought has just 2 plugs--the left on is bigger and I think is the neutral.
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One of them is supposed to be neutral, but it will be live if your receptacle was wired by a drunk electrician. Treat both wires like they are live and switch both.

I know, let's treat the earth as though it's live and switch it too, just in case the socket was wired by a drunk electrician. ;D
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Hi Alun,
In North America, many appliances and electrical cords have only two wires, live and neutral. There is not a ground wire so their switch is DPDT to cutoff both wires in case the receptacle was wired wrong.

Electricians are human (I think?) and make mistakes. I was in a building under construction and the electrical inspector loaded the sytem and was taking infrared photos of the breaker panels. The wire connections that overheated were clearly shown and had to be re-done properly. ;D

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I live in the US and the cord I bought has just 2 plugs--the left on is bigger and I think is the neutral.
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In the case that you do have two different sized prongs, it is the same wiring as the picture below. It might not have the round ground prong, but wiring is the same.
(The Neutral, Ground, and screw in the center should all be common to each other.)

MP

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