Question about current draw

[OldEastRR]

With a DCC system, does the amount of current drop when there is a load on the circuit? I know just plain voltage is 11.5 or something --- but if you've got 2 or 3 locos running, with strings of track-lighted passenger cars?

[Maletrain]

I don't think the voltage will drop much at the output of the command station and/or boosters.

But, there will clearly be some voltage drop in the wires and rails, and that is dependent on the length of the circuit and sizes of the wires and resistance in the rail joiner joints.

That is why the "quarter test" (a low resistance short across the rails) is recommended for all locations on the layout, to make sure that there is not so much resistance to some place that the booster's nominal voltage is not sufficient to drive its breaker trip current to that location against the resistance between it and the booster.  The voltage across the rails is essentially zero where they are bridged by a quarter.

[jagged ben]

With a DCC system, does the amount of current drop when there is a load on the circuit? ...

No.  The basic concept is that more load means more current, not less. 

I think Maletrain assumed you must be asking about voltage dropping instead of current, because that can be a thing with increased load.   If the voltage drops then the current does too, but that is more a function of the power supply or the track wiring, not the number of locomotives and passenger cars per se.

Maybe clarify what problem you're trying to solve or phenomenon you're trying to understand.

[kwledbetter]

Assuming you are using a good regulated power supply then the only voltage drops will be the electronics producing the DCC signal (this will be significant typically 1-2 volts) , and the transmission drop aka how long the wire run is from the decoder, and wire size.