Basic Home Electrical Question

[Bill]

Polarized plugs are a safety feature, especially with something like a lamp. This connects the "hot" wire to the center connection where the bulb screws in.

When replacing a light bulb, it is possible you could accidentally touch the metal ring while unscrewing the bulb. If the metal ring is connected to neutral (because of the polarized plug), then you will not get shocked.

Also the polarized plug will connect to an appliance on/off switch. So when the appliance is switched off, it is shutting off the hot. So say something like a toaster which has a switch which only disconnects one wire. It is best if the wire the switch is disconnecting is the hot wire! Otherwise hot would be connected to the heating elements even when the toaster was off, and a kid might stick a knife or hand inside the toaster, then be shocked.

[RBM]

No, it has already gone through a resistor. It's a return seeking its neutral or ground to complete its circuit, and this fella needs to understand that if he gets in between it he's going to get hurt.

[Rich Greenberg]

Yes, as long as you are not in contact with a hot line.

In fact, if you are careful not be be grounded you can touch the hot wire without a shock. I don't recommend doing this, but I have changed both switches and outlets while they were live.

[Toller]

Certainly, but only because the live end of the white wire is now a hot rather than a neutral.

[RBM]

[Toller]

Sure, it has been through a resistor (or at least a load of some kind...) so why isn't it still a hot? Take a 240v motor. It has three wires; 2 hots and a neutral. A hot goes to a winding and then to the neutral. When it comes off the winding it is not a neutral, it is simply a hot that has gone through the winding.

This is hair splitting; we certainly agree that the wire, whatever it is called, is potentially dangerous. But, I think it is still properly called a hot.

[Ralph Mowery]

A normal 240 volt motor only has 2 'hot' wires. There is no neutral. Both of the wires are 120 volts hot to ground in a normal home in the US. It may (should) have a ground wire going to its frame.

[Chris Lewis]

According to RBM :

Right.

Still, for all intents and purposes it is a hot. You're not going to find a significant difference between the lethality or voltage of a direct-from-panel hot, and one that's gone through a lightbulb on the way (if it's disconnected from neutral).

[Colbyt]

I just love this group when you guys get in a spirited discussion about something so far removed from a direct answer to the question.

Too much schooling I guess.

[Stormin Mormon]

Nothing silly about being safe.

[Art Greenberg]

There are actually three conductors in house wiring; hot, neutral, and ground. Only the hot and neutral wires are intended to carry any current. The gound wire is a safety device. It is connected to your cold water pipe, to any exposed metal in powered appliances (hence the three prong plug), and to the earth itself. And, at your main circuit panel, it is connected to the neutral wire. If the wiring is correct and functioning as intended, you should only be able to observe (via a meter) a voltage difference between the hot conductor and *either* the neutral or ground conductors.

These designations, and the way the safety system functions, are completely independent of whether the system is driven with direct current (DC) or alternating current (AC).