Look up or Google this: National Electrical Code Table 310.16 This is the table you are looking for. You can find a link by following the related question below.
140 AMPS
3/0 gauge
Yes, # 4 AWG copper and 100 amps is the max.
Typically 30 amps.
The American Wire Gauge code table shows 8 gauge safe for 24 Amps, 10 Gauge for 15 Amps. If the circuit is going to be used at capacity (2400 Watts in this case), 8 or 10 gauge is the minimum, if load is constant, use 8 gauge. Voltage ability of the wire is dependent on the insulation thickness and material. So 20 amps at 120 Volts is 2400 watts of power, and 20 amps at 12 volts is 48 watts of power. Both would require the same gauge of wire, but the higher voltage would need better insulation. <<>> This is a voltage drop question. A #1 copper conductor will limit the voltage drop to 3% or less when supplying 20 amps for 500 feet on a 120 volt system.
50 amps
In cooper electrical wire, gauge 8 means the wire size assigned by the American Wire Gauge (AWG) system. That is why you always will hear about AWG WIRE, it's not the type of wire is the gauge that we are talking about. A gauge 8 wire will be used for connections requiring from 40-45 amps to a maximum of 73 amps. (24 for power transmission). Diameter of an 8 AWG wire is 0.12849 inches. 8 AWG is solid, not stranded.
The amps that a four gauge wire will handle will depend with the thickness of the wire. If the wire is thin, the four gauge will handle 95 amps.
Amps is short for ampere, a unit for current.
140 AMPS
I am assuming that this is a one and a half HP motor. To wire a 120V 20A motor the electrical code states that the conductor has to be 125% of the motor's full load amps. This equals 25 amps. There is no wire rated at 25 amps so the next size up is 30 amps. A #10 copper wire with an insulation factor of 60, 75 and 90 degrees C is rated at 30 amps. To carry this to a conclusion This #10 wire should be protected by either 60 amp non time delay fuses or 35 amp time delay fuses or a two pole 50 amp breaker.
The electrical current in a circuit is measured in amps.
70 amps.
15 amps
This is a voltage drop question. To answer this question an amperage is needed.
3/0 gauge
50 amps