it's pretty destructive.
30k rpm and 7.2 volts at like 5 amps?
destructive.
counter EMF is also called back EMF. it's a product of the generator effect that a coil has in a magnetic feild. it's an AC charge. back EMF also limits the motors top-speed. there's more back EMF in lower rpm motors, resulting in a slower spinning motor, but in both high-speed and low-speed motors at their topspeed, the back EMF equals the energy that is put into making it spin. this is called equilibrium. the net acceleration is zero since the back EMF has countered all of the force that is used to accelerate.
back EMF increases in proportion to rotor speed.
the spiral arm reduces back EMF by producing a weaker magnetic feild, allowing a higher speed before reaching equilibrium.
if not for back EMF, then a stage 1 motor could reach an infinite amount of RPM at any voltage
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