I have checked How Stuff Work, About.com, Ask.com, Google and even asked an electrical engineer and found no satisfying answer to the following questions: For household AC current, why do we need 2 live, a neutral and a ground 4-wire connection? We get 3 wires from the street transformer where the Secondary coming towards home has a middle tap. The phase difference from either one end to the middle tap of the Secondary is 120 volts, and end-to-end 220 volts. We use one of the single phases for the light bulbs and toasters (110V) etc. and we use both phases for the Central Air Conditioner (220V). If you hookup a light bulb only with the live wire and use the ground instead of the neutral wire, it still lights up. I know power companies use the planet's ground as a wire to return electrons. The middle tap for the 2-phase Secondary which is coming to the home can be grounded, can it not? Since the neutral wire and the ground wire both are used for returning the electrons, why don't we just use the live wire and the ground wire and no neutral wire for single phase appliances? Why do we need the separate neutral wire for a single phase 120 volt light bulb?