Final answer:
Both Technician A and Technician B are incorrect. A three-wire device is typically a potentiometer, not a rheostat, and a two-wire device could be a two-terminal rheostat. The correct answer is (A) Neither A nor B.
Step-by-step explanation:
The question is in regard to the identification of the types of variable resistors based on the number of wires they have. Technician A suggests that a mechanical variable resistor with three wires is likely a rheostat, while Technician B suggests that a variable resistor with two wires is likely a potentiometer.
A rheostat is usually a two terminal device, but it can have a third wire connected to one of the terminals to preserve the full resistance value, essentially making it a three-wire device.
On the other hand, potentiometers generally have three terminals, one for the variable wiper and two for the ends of the resistance element. Considering the standard configuration of these devices, both Technician A and Technician B are incorrect because a three-wire device is more indicative of a potentiometer, not a rheostat, and a two-wire device could be simply a two-terminal rheostat.
Therefore, the correct answer is: (A) Neither A nor B.