Sully75- there are two issues relating to wire size, voltage drop and ampacity. A short piece of small wire will probably not result in significant voltage drop. However, it will have a lower current
limit (ampacity) and will require a smaller circuit breaker or fuse to protect against fire. To explain, the smaller wire will heat up from the relatively large current
that could easily be conducted through the larger supply cable, and if this heat exceeds the temperature rating of the wire's insulation
it can melt the insulation
or even start a fire. Thus the circuit breaker must be sized to protect at the maximum current allowed through the smaller wire, no matter how short. This will limit the current that can be allowed on the entire branch, unless the device has its own fuse or breaker.