Adjust load resistance on right, within operating range, the unregulated supply voltage doesnt change. Purpose is to design current limiting circuit that will actively limit load current regardless of load resistance. Also important is lowest power dissipation in limiting device. Minimum mosfet dissipation occurs when load resistance is adjusted to a value with minimum voltage across fet at maximum current flow. This circuit wastes about 35W using mosfet. A similar design using BJT is slightly more efficient coming in at about 33W. (power dissipation in resistor above source on left is not important since it represents a varying internal resistance of source.)
