In the car train layout!

Rheostats were the way we controlled speed before all the solid state electronics  happened. Voltage out is load dependent and not certain how well they would work with N. When transistors became available a slew of transistorized throttles were developed and written about in the magazines in the 60's.  Do an internet search and you're sure to find something simple. Try this web site for a starter

transistor throttle circuits

Scotie

Yes it will work.

With N I think you draw a light amp load. An old dimmer control for a cars dashboard lights may handle the load. I say old because many old cars have a higher amp rating; they were lit like Christmas trees