Stepper motor limiting current
After writing this I see that it MAY be homework" or similar.
The following is fairly basic as far as stepper motors are concerned and should be in any notes associated with a relevant course or in text book. What is the context of this question?



Limiting current is simply voltage / resistance = Ohms law.
I = V/R = 12/20.5 ~= 0.6A

Time constant = L/R = 0.045H / 20.5 Ohm ~+ 2 ms.
It would take several time constants for the current to approach the limiting value which is set by Ohms law.