The high ohmic series resistor is the internal resistance (Rin) and the Potentiometer is considered as the load
The current is nearly constant when the potentiometer is varying
It's because the internal resistance is high enough, so it dominates the circuit and only causes minor changes
To create an impact
The load resistance ≥ 0.01*Rin
In our case, Rin=1MΩ
So, R(load) ≥ 0.01*1MΩ ≥ 10KΩ
The region where the current changes minorly when the load resistance is varying is known as
Stiff region of current source
This is for testing purpose
