What is an electric shared neutral?
An electric shared neutral is the white or negative wire that is shared between two electrical circuits on a basic single phase system. Most electrical devices use 120 volts and require a "hot" wire and a neutral wire to operate. Some larger devices use 240 volts and require two "hot" wires to operate. Two circuit breakers in an electrical panel can share one neutral wire as long as the breakers are not on the same "leg" of power. When looking at an electrical panel there are usually two "legs" of power feeding all the breakers, each leg has 120 Volts to ground, if the "legs" are combined you will have 240 Volts. A neutral wire can be shared by two circuits as long as the breakers are on separate "legs". If someone needed to add two circuits in their home, the could run what is called a 3-wire romex, It has a black wire, a red wire, a white wire and a ground wire. The white wire is the neutral for both the black and red 120 volt circuits, and the breakers for the new circuits would need to be on separate "legs" in the panel.
When using 10 2 wire for a 3 wire dryer can the neutral wire be the unshielded ground wire or does it have to be shielded?
If your electric dryer (meaning the heating element is electric, not gas) has a neutral you need 4 conductors: 2 are hot, 1 is neutral, one is ground. Neutral should always be insulated. If your electric dryer does not have a neutral you need 3 conductors: 2 are hot, one is ground The ground in either case can be bare.