What is Rm stands for and what does it mean?

Question

Here is the website about the motor effeciency http://www.peakeff.com/GraphKIR.aspx

Answer 1

Seems to be the resistance of the motor. Set the resistance to the same as the voltage and the max current becomes 1A. Since it's DC and V=RI V/R=I so 10.4/10.5=1 which is what gets shown on the graph.

Sorry, it's just an educated guess from an engineer.