To answer this question the voltage and load amperage is needed.
It depends on the length of the run
I would use AWG # 4 copper.
If this question is asking about voltage drop, to size a wire, a voltage is needed.
14 AWG is fine for this application.
for residential use 2/0 copper or 4/0 aluminum, if your talking long distances then you need to up size for voltage drop
12 gauge or bigger.
It depends on the length of the run
you must run the proper size wire based on the ampacity needed, wire must have four conductors including the gound
Normally AWG #10 wire on a 30 amp breaker but it really depends on the size of the pump. The pump manufacture will specify the size wire and size breaker needed.
I would use AWG # 4 copper.
14 AWG is fine for this application.
If this question is asking about voltage drop, to size a wire, a voltage is needed.
This is a voltage drop question. To answer this question a voltage must be stated.
12/3 will work.
If it is a 110 volt light it can safely run on a 20 amp circuit with AWG # 12 wire.
Presuming that you would like the least expensive installation, the following is calculated on overhead aluminum wire. The wire size needed to hold the voltage drop to 3% would be 3/0 MCM. If the installation could be run on 240 volts then the wire size can be reduced to #2.
The wire size depends on the amperage, not the voltage. The fact that the welder runs on 440 volts does not affect the wire size! You need to ask this question instead: What size wire do you need for a three phase welder on an eight foot run if the nameplate amps are 45A?