Which term matches the definition: a rotary magnetic or dynamo-electric amplifier used in servomechanism and control applications?

• A. Amplidyne
• B. Amplification
• C. Amplifier
• D. Arc

Answer: (A)

An amplidyne is a high-gain power device used in servo and control systems. It’s a rotary dynamo-electric amplifier, meaning a small input signal controls the magnetic field of a generator that is mechanically coupled to a rotor, and the generator’s action feeds a much larger current to the load through rotating rectifiers. This arrangement provides a large output current from a relatively small control signal, which is exactly what servomechanisms need for precise, powerful actuation.

That’s why the term fits best: it describes a specific rotary, dyno-electric amplifier used for boosting control signals into large actuator outputs. The other terms are more general—the process of increasing signal strength, a generic amplifier, or an unrelated electrical arc.