A #6 copper conductor is rated at 65 amps. To connect to a 50 amp RV outlet you will need a four conductor #6 SOW 600 volt cabtire. The black and red wires go on terminals X and Y. The white wire goes on terminal W. The green wire goes on terminal G.
The minimum size wire that engineers spec for industrial and commercial installations is #12 and it usually is stranded not solid wire.
Assuming this is not an office of a place where lots of the outlets will be used to power items that draw lots of current on a 15 amp circuit wired with 14/2 wire I would limit it to no more than 10 outlets and lights combined. On a 20 amp circuit wired with 12/2 wire I would limit it to a 14 outlets and lights combined. There is no limit in the code. You just use common sense based on what is going to be used on this circuit.
Older style wires and cables are not as safe as the current types used for house wiring. For example, older insulation becomes brittle with age and can break when the wire is moved. Newer wiring is a lot more flexible and can handle age much better than the old insulation. Newer wiring specifications require that all circuits include a connection to ground, older outlets do not have that requirement. Newer outlets are far safer, not just because of the ground wire but because of the plug polarity that has been introduced to the newer standard.
As with any electrical installation, the wire size used depends on the expected maximum current the wire will carry. That cannot be determined by voltage alone.
14-3 Is the standard wire use for residental smoke detectors.
It is unusual to have multiple outlets on a 30 Amp service. If you do this you need outlets rated at 30 amps and 10 AWG wire.
Yes. It is abbreviated as AWG. For example, in residential wiring the size wire to use on a 15 Amp circuit would be 14 gauge or 14 AWG.
The wire size is dependent upon the wattage size of your water heater. The higher the wattage the larger the wire size. A standard 3000 watt heater will use a two pole 20 amp breaker connected to 2C #12 wire.
A. It's 240 volts & B. Wire size is a function of amperage. 12-gauge wire is used with 20 amperes or less. So, 12-gauge wire can be used with 120V/20A or 240V/20A. Keep in mind though that 240V in the U.S. has 2 live 120V lines so if you encounter a white wire, it's probably an unmarked live & should be repainted as black or better yet, red (to indicate the 2nd live wire).
A 15 amp breaker protecting # 14 wire.
It is metric that is used in the European standard of wire measurement.
The same way
For a standard clothes dryer, new homes are roughed in with 3C #10 cable which is rated at 30 amps.
The frequency has no direct relationship to the size of wire. Wire is sized as to the amount of current a load draws in a circuit.
Not if it is secured and tightened properly and has the correct size breaker installed for the wire size used.
The minimum size wire that engineers spec for industrial and commercial installations is #12 and it usually is stranded not solid wire.
Copper is preferable to aluminum and the size of wire should be the same or the next size down if copper is used.