There is also a standard wiring convention used when wiring the plugs, receptacles and terminal blocks of 220 volt appliances, all of which will have provision for connecting THREE wires as well as a ground wire. Normally the ground wire terminal will be easy to identify because it will be grounded to the electrical box by an electrical conductor, and the remaining three connection points for the red, white and black wires will be arranged in a row. The wiring convention is that the white neutral wire is ALWAYS connected to the middle terminal in that row of three connection sites, and the red and black wires are connected on either side of it. It doesn't matter which side you connect the red or the black wires to, as long as the white is in the middle and the red and black are on the outside, you're good to go. If your stove or dryer doesn't come with a cord and you want to connect one to the terminal block of the appliance, the same rule applies, namely "white in the middle, black and red on the outside". If you're wanting to wire a receptacle for a stove or electric dryer, then again, the same rule applies. First identify the ground wire terminal, and the remaining three connection points will be for the red, white and black wires and they should be arranged in a recognizable "row". Always connect the white in the middle of those three sites and the red and black on either side of the white. This point has now been officially hammered into your head; white in the middle, black and red on either side.
Every dryer cord will have 4 prongs sticking out of it. The straight ones are for the red and black wires, the "L" shaped one is for the white wire and the round one is for the ground wire. Range cords also have 4 prongs, but they will use 3 straight prongs for the red, black and white wires and a round one for the ground wire. Configuring the plug and receptacle differently (with an "L" shaped prong instead of a straight one) is done so you can't stick a 30 amp dryer plug into a 50 amp range receptacle or vice versa.
The heating elements in both electric dryers and stoves require 220 volt power, but you still need to run the white wire to the stove or dryer. The reason why is that there will be circuits within the stove or dryer that require only 110 volt power. For example, the electric motor that turns the dryer drum or the light bulb inside an oven will both require 110 volt AC power, not 220 volt power. So, in an electric stove the heating elements will be connected between the red and black wires because they need 220 volts, but the electrical outlets provided for convenience on the stove console will be connected between the white wire and either the red or black power wires, because the convenience outlet is intended to provide power to 110 volt appliances. And, this is also why you can have TWO convenience outlets on a stove instead of just one. One of those convenience outlets will be powered by the black wire, and the other one by the red wire. Since the main black and red wires going to a stove are fused at 50 amps each in the electrical panel, any circuit between the red and white OR black and white wires in the stove will give you a 110 volt 50 AMP CIRCUIT which probably won't stop pumping out the electricity if there's a short somewhere in that circuit, and 50 amps going through wiring rated at 15 amps is a great way to start a fire. That's why for the electric outlets provided for convenience on range cooktops, there will be a 15 amp fuse right in the range somewhere that fuses each convenience outlet down to 15 amps. If you have two cooktop plugs, one will be driven by the red wire and one by the black wire, and each will have a separate 15 amp fuse on it.
Also, if you stop to think about it, if the black supply wire is feeding a 110 AC voltage sine wave into the white "return" wire and the red "supply" wire is also feeding an equal but opposite voltage into that same white "return" wire, then theoretically, there should be no voltage in the white wire since the two sine waves would cancel out. Similarily, the resultant current sine waves from the red and black wires would cancel each other out when they both meet at the white "return" wire. If the world was perfect and all electrical loads were purely resistive, like light bulbs, toasters, electric ranges and coffee makers, then the voltage and current sine waves from the two power supply wires would indeed cancel each other out, and there would be theoretically be ZERO voltage and ZERO current in the white wire. However, the world isn't perfect, and professional wrestling isn't real and Lassie has started killing chickens. In the real world there are electric motors and television sets and computer monitors, all of which have some "impedance". In an electric motor, for example, the magnetic fields created by the electric motor windings impeded the flow of current through those same motor windings, so the motor windings themselves cause the current sine wave coming out of the motor to lag behind the applied voltage sine wave. Also, television sets and those old CRT style computer monitors have huge capacitors in them. In a capacitor, the current OUT of the capacitor is highest when the rate of CHANGE in voltage is highest, and that occurs when the voltage sine wave passes through the point of ZERO voltage. Thus, capacitors cause the current sine wave coming out of those computer monitors and TV sets to actually preceed the applied voltage sine wave. So, even though the red and black wires carry equal and opposite 110 AC voltage sine waves, the impedance of "reactive" loads like electric motors and TV sets causes timing differences in the resulting current sine waves coming out of those loads. So, the current and voltage sine waves generally DON'T cancel out in the white wire, and there can be significant voltages and currents in the white wire. So, to be safe, treat every wire as having dangerous voltage in it.
