Can someone explain the neutral wire in AC electricity to me?

Question

I understand the main idea in AC electricity is that the current is moving back and forth. Why in a lamp is one wire hot and one wire neutral? Shouldn't they both be the same?

Answer 1

The neutral wire has nothing to do with "three phase" electricitiy. At the transformer on the pole outside the house, there is a coil, and the voltage measured between the ends of this coil is 240V AC, meaning that the voltage difference measured between these wires fluctuates 60 times a second, ranging from +339V to -339V (the 240 nominal voltage is an average). There is third wire (the neutral) connected to the middle of this coil, and the voltage between this wire and one of the ends ranges from +169 to -169, while between this wire and the other end it ranges from -169 to +169. That is, when the center and the left end are 169 apart, the center and right end are -169 apart. (Again, 169 is an average, the nominal voltage is 120). The three wires come into the house, and the neutral wire is connected to the ground both at the pole and in the house (water pipe, stake in the dirt, etc). If you now hook your toaster to the left wire and neutral, the current flows back and forth into the toaster on one wire and out of the toaster on the other wire. IF, however, you now hook your steam iron to the right wire and neutral, the current flows as before, but since the left and right wires have opposite phase (remember, -+ versus +-), there will actually be no current flowing on the neutral wire. The two out-of-phase flows cancel each other out. This is why the wire is referred to as "neutral"--if loads are exactly balanced, there is no current flow along it. The fact that it is grounded is basically irrelevant to this situation, and not all systems of electrical distribution use a grounded neutral, if indeed they have a neutral at all. In Europe, for instance, there is no neutral wire.

Answer 2

The difference between the "hot" wire and the neutral has nothing to do with the fact that the wires are carrying AC current. Rather, the neutral wire is electrically connected to the ground at some point, whereas the hot wire is (or can be) connected to the power supply mains.

Although both wires carry the same amount of current in a properly functioning circuit, hot wires and the conductors to which they are connected must be carefully insulated to avoid a shock hazard. Neutral wires, on the other hand, are nearly at ground potential. If it weren't for the fact that even conductors have some resistance and inductive reactance, the neutral wires would be at ground potential.

For safety's sake, it is important that any functioning part of the circuit exposed to contact be connected to the neutral side of the circuit. The design of household incandescent light bulbs is such that it is possible to touch them while in operation. In the olden days before everything had polarized or grounded plugs, it was possible to plug such a light into the wall so that this base might be connected to the hot side of the circuit. I got a buzz a few times as a child when I went to turn off a light and got against this base by accident.

It is also important for safety that the connection between ground and neutral be maintained unless it can be guaranteed that the connection to the hot side is also broken when the neutral is disconnected from ground. For this reason, switches are always connected on the hot side of the circuit except double throw types where both sides of the circuit are switched.

Because the voltages encountered in automotive wiring are not high enough to present a shock hazard (with some exceptions) the neutral wires in cars are usually dispensed with and the current returns through the body of the car itself.

Answer 3

in a wire is a hot and neutral, the same wires run from the panel to your lamp. the electricity going into your lamp has to feed back out as well. this is called a circuit. the electricity comes out of the panel on the hot and trvels through your lamp. since it has to complete the circuit, the electricity travels back to the panel through the neutral wire. if there were no neutral wire this process could never take place and your lamp would not work.

Answer 4

Neutral is (usually) grounded at the transformer secondary that brings power into your house, but is not as safe to touch as the green ground wire since it carries the full return current of the appliance. It develops a voltage at the appliance while on equal to the current of the appliance times the resistance of the neutral wire between the appliance and the transformer. It only has zero voltage when there are *no* appliances on that circuit (not just one in the outlet you're working on).

Answer 5

The reason for this is phasing. Because AC uses alternating currents three wires are needed for the various portions of the 3 phase cycle. I have included a couple of links below that are rather in depth reads but explain it well.

It all boils down to the fact that three phase is more efficient and can deliver more power then single phase which would require only 2 lines.

Answer 6

well ac supply is totally different from dc....in ac only one wire carry the supply that is the phase wire while the neutral wire carry the same back from the consumer.....so the direction of flow of current in the two is totally opposite.....so if the neutral wire is not connected to load but is connection to the main then it will be carrying no current...........