I am wiring a barn/shop fed by a 100 amp service. Some of the outlets may be over 70 feet from the panel (all will be 20 amp breakers). Should the wire size I pull in for these outlets be 10awg rather than the normal 12awg? My question relates to voltage drop. The shop is about 50'x 70'. Two big stalls with a shop in the middle. Would it make since to put a subpanel in the shop area? The shop is about 40' from where the service panel is located.
Thank you
Guy

As Tesla showed in his day... Alternating Current does not loose power over distance, except miles and miles - that's when the voltage is increased to facilitate more effective power transmission. So that is not an issue in your case.
A sub-panel is an opportunity to bring a single but fatter wire over a distance and then distribute this power to more stations without running a lot of long wires back to the original panel. It's also safer. It's a judgement call in my opinion unless there is code involved. I know little about code ! If it was me I'd put in the sub-panel. A shop usually needs a lot of outlets. I think 3 per 20-amp breaker. Larger pieces of equipment such as table saws should be powered by dedicated circuits. It's best to wire lights, so that they are on a separate circuit from the wall outlets. If a tool trips a breaker, the lights will remain on since they are on a separate circuit. If you need tools that draw 240V, then I think you definitely need a panel. I'm not a pro - so you'd be wise to get more opinions..

Voltage drop is an issue with voltages of 120 and 240 volts and the small branch circuit wiring typically installed.


NEC requires that circuit design take all the factors in consideration to eliminate any voltage drop , with the recommended allowance of 3% for feeders and 2% for branch circuits, and not more than 5% overall.


If the 20 amp circuit is loaded to it's full allowed capacity of 16 amps,a t 70 feet and 120 volts, the voltage drop will be 4.3 volts dropped. This exceeds the recommended 2%, or 2.4 volts, of Vd for a branch circuit. So if the 20 amp circuits will likely be loaded 16 amps, #10 wire would be recommended.

Installing the "subpanel", technically called a loadcenter, for obvious reasons, may be a good idea to reduce the length of branch circuits, and eliminate the necessity of larger wire for branch circuits. Using # 10 on a 15 or 20 amp receptacle and switches becomes a real challenge for good tight connections.