The way I understand it, it's very similar to "Fluid hydraulics" (i.e. pumping fire apparatus). Can you get X amount of water (Gallons Per Minute) through Y hose that is Z feet long? How much energy (Friction Loss in psi) will it take to accomplish this?
Example - 175 GPM through 50' of 2.5" hose takes 3 psi FL to do this, which must be included when calc'ing your pump pressure.
To push twice as much water through (350 GPM), it takes four times as much energy (12 Psi).
In fire engineering, it's not the pressure, it's the GPM. Just like wiring - it's not the voltage, it's the amperage.
Can you get 15A through 14ga AWG CU? Sure.
Can you get 30A through 14ga AWG CU? Sure, but the wire will heat up beyond the design specifications of the insulation (safe operating temp), and it creates a hazard. And, just like hose, the more you try to push through it (GPM/A), the more if will fight the flow (FL/R).
