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The idea of this question came from a DC motor that produces less torque by greater speed.
For question #2 as far as I know \$ F = \frac{k Q_1Q_2}{r^2} \$ and the current will flow while charging/discharging the rotor.
Note: Referece motor for my question youtube video.
THis is picture capture from video.
There are many types and configurations of electromagnetic motors. Many of those configurations can be operated in a way that the motor has the capacity to produce constant torque with variable speed over a substantial speed range.
Electrostatic motors are generally duals of various types of electromagnetic motors. As a dual, various aspects of an electrostatic motor are reversed with respect to their electromagnetic duals. In electromagnetic motors, speed is generally proportional to armature voltage and torque is generally proportional to armature current. In electrostatic motors, armature current is proportional to speed and armature voltage is proportional to torque. Electrostatic motors have some capability for constant torque with variable speed.
There are technical papers describing current and recent electrostatic motor research. Some of them may be openly available. I will see what I can find.
I believe these are open source:
SEMs have declining torque with increasing RPM just like magnetic ones but can be only 5% of the stall power at the same torque at 0 RPM.
But what they consider “medium voltage” 5kV for electrostatics we consider Ultra High conductors for semiconductors , so speed control or constant torque using transistors in thus range are worth a hundred bucks because of the overkill on current ratings.
So your torque is not constant with RPM.
I wonder if the e in SEM’s are excited or electrostatic. (Lol) but 5kV would be exciting with partial discharge sparks flying thru the dust. It could kill a thousand mosquitoes per second.
Ref ixys/IXTL2N470/
The inversely proportional relationship between torque and speed is universal and can never change.
Torque = Power/Speed (T=P/ω)
At constant power, there would be increasing torque with decreasing speed and vice versa.
In any motor, torque would remain constant as the speed is reduced, should the power also be simultaneously reduced, and vice versa.
A VFD controlled induction motor is one such example. 'V/f' would remain constant up to the rated speed after which 'V' would remain constant at the rated voltage and 'f' would continue to increase. Thus there would be a linear increase in power, with the torque remaining constant up to the rated speed, after which the power would remain constant and the torque would drop.
The behaviour would be the same with a DC motor having 'armature control' up to the rated speed and 'field weakening' after that.
