Velocity uniformity of rotation in dynamos and DC motors.

[Entanglement]

How can velocity uniformity in dynamos and motors be explained?
What's the mechanism of that happening ?
I'm aware that Newton's first law is involved in that situation where an equal and opposite torque must act on the coil during its rotation so the net torque is Zero and the coil keeps rotating with a uniform velocity,
But the mechanism seem quite confusing that needs some clarification, thanks a lot PF in advance.

 

[Simon Bridge]

Start by writing down why you would expect anything else: what were you expecting would happen?
Then also consider how you know the rotation is uniform ... perhaps it varies a little bit?
The answers to these questions will help us to best answer you, and may help you answer your own question to boot.

Note: Newton's first law would not indicate that an equal and opposite torque would act ... "equal and opposite" is part of the wording of the 3rd law ... but that also does not apply here: reaction forces do not prevent acceleration. Is it possible that this question arises from common misunderstandings about Newton's laws?

A dynamo would be a kind of electric generator - as such, it is usually turned by something else. Thus any uniformity in it's motion will be a reflection of the motion of whatever is turning it. So I don't see much mystery there.