If household current is AC, why are so many plugs polarized?
The polarization has nothing to do with the polarity of the circuit, as in DC circuits, but it has everything to do with safety. Your home (assuming you live in North America, other locations have equivalents) is connected to a 240 VAC two-phase mains supply, with two hot circuits and a neutral return. The two hot circuits are 120 VAC each and operate 180 degrees out of phase with one another. One half of the electrical panel is fed with one phase and the other half with the other phase. This provides your home with two 120 VAC single phase circuits and the ability to power 240 VAC appliances. Each household circuit uses three wires: hot, neutral, and ground. The ground wire is physically tied to earth somewhere in your home, often to a buried copper rod or to the water supply main. The neutral wire in the circuit connects back to the mains neutral and is tied to ground inside the electrical panel. The hot circuit connects to one of the two 120 VAC circuits. The plugs and outlets are p
