Final answer:
Technician B is right; a transistor amplifies current in a circuit by acting as a 'valve' that controls the flow of a larger collector current when a smaller base current is applied.
Step-by-step explanation:
Technician B is correct; a transistor is primarily a device used to amplify current in a circuit. A junction transistor, for example, comprises an n-type semiconductor (emitter), a p-type semiconductor (base), and another n-type semiconductor (collector). Applying a small current to the base, known as the base current IB, can control a larger collector current Ic. The base current regulates the collector current, essentially acting as a 'valve' that can be opened to various degrees, allowing the transistor to amplify the current flowing through a circuit. This characteristic makes transistors essential components in amplification applications, such as loudspeakers and radios. While transistors can be incorporated into circuits that rectify current, like a diode does, that is not their primary function.