I should really know this question. It's a basic electronic and physic's question. I am going to give it stabe at it. A motor just like a light bulb has no polarity to make it work. Polarity is used in DC circuits. You have a positive and negative. Ac has no true polarity. If you connect AC to a scope (oscilloscope) you will see a sin wave. You do the same thing to DC. You will get a flat wave. By the way, if you turn on and off DC to a scope. You have created a square wave. This is basic function off ALL computers!:thumb:
Now back to the motor. A motor has no polarity. It doesn't matter which way it's on the tracks. If the DC hasn't change. Nor will the direction of the locomotive. No matter which way it is placed on the track.
NOW! If you change the polarity of the track. It will change the direction of the locomotive. The winding of wire inside the motor makes this work. When you change the polarity of the track. You also change the electromagnetic field of the motor.
In Electronic Theory States: The Protron (positive) will flow to the Eletron (Negative)
In Eletron Theory State: The Electron will flow to the Protron.
Please not only crazy engineers will use the Eletron Theory when it comes to electronics. Almost everyone uses the Electronic Theory.
I hope I didn't confuse anyone with this.
Andy