variable power ""resistor""

law battery. 2 JL 125 NIV which may prove to be a little high for the 28 variable power "resistor A major difficulty encountered when testing power supplies is the availability (or non-availability) of a suitable load. usually, the problem is solved by a lash-up of resistors which, although not particularlY elegant, will enable tests to be carried out. However, resistors with a power rating of 10 Watts and upwards can be rather expensive and certain values difficult to obtain. Furthermore, this type of load will not be variable. The simple circuit described here can overcome these problems effectively and economically. A 2N3055 transistor with a variable gain controlled by an indePendant supply will form an infinitely variable load "resistor". This circuit will have a power capability of up to 50 Watts if a suitable heat sink is used. The ability to maintain a fixed load current when the power supply output voltage is varied is an added advantage. The maximum dissipation of the tr...