A #14 copper conductor is rated at 15 amps.
It will take 2-gauge cable. This high current cable is usually called service entrance cable. Service entrance cable is usually 1-gauge so it is easier to find and cheaper to buy than 2-gauge cable.
This is an aluminum clad cable with black plastic sheathing.
#4 copper
12 AWG in most circumstances.
40 amp
You use the correct size breaker depending on the size wire in the circuit. If the circuit is wired with AWG #12 wire use a 20 amp breaker. If it is wired with AWG #14 wire then use a 15 amp breaker.
A #14 wire will do fine for grounding a 20 amp device. That is the size of the ground wire in a 2 conductor # 12 wire building cable.
Yes, they are the same size wire.
AWG # 10
12 AWG in most circumstances.
40 amp
You use the correct size breaker depending on the size wire in the circuit. If the circuit is wired with AWG #12 wire use a 20 amp breaker. If it is wired with AWG #14 wire then use a 15 amp breaker.
30 amp breaker with #10 gauge copper wire
2.5 squre mm
25 amp breaker
Typical residential electric dryers are on 30 amp circuits, which means 10 gage copper wire. The circuit breaker should match the dryer cord rating, generally 30 amps.
A 100 amp residential service requires a size #8 copper wire, it should be insulated in green.
The size breaker you use is determined by the size wire used in the circuit. If you use AWG #12/2 wire then use a 20 amp breaker. If you use AWG # 14/2 then use a 15 amp breaker.
Don't use aluminum wire inside the house.
A #14 wire will do fine for grounding a 20 amp device. That is the size of the ground wire in a 2 conductor # 12 wire building cable.