Identify device with a plunger (movable iron core) Which electromagnetic device uses a cylindrical iron plunger that moves when the coil is energized?

Introduction / Context:
Electromagnetic actuators convert electrical energy into mechanical motion. The terms “relay” and “solenoid” are often used loosely, but a solenoid specifically refers to a coil that creates a linear motion of a ferromagnetic plunger or armature when energized.

Given Data / Assumptions:

• Movable iron core (plunger) feature highlighted.
• We contrast with speaker, DC generator, and relay.
• Assume conventional electromechanical constructions.

Concept / Approach:
Energizing a solenoid coil establishes a magnetic field that pulls a ferromagnetic plunger into the coil, producing linear motion used for latching, valves, and push-pull mechanisms. While many relays also move an armature, the classic plunger configuration with a tubular coil is emblematic of a solenoid actuator, not a loudspeaker or DC generator.

Step-by-Step Solution:
Identify the key hallmark: a sliding ferromagnetic plunger drawn into a coil.Map the hallmark to device type: characteristic of solenoids.Differentiate: a relay moves contacts via a levered armature; a speaker moves a cone with a voice coil; a DC generator rotates an armature.Select: “A solenoid.”

Verification / Alternative check:
Product datasheets for linear solenoids show coil, sleeve, and plunger assemblies designed for strokes in millimeters to centimeters, confirming the definition.

Why Other Options Are Wrong:
Speaker: has a flexible cone and voice coil, not a plunger.DC generator: rotary device with commutator and brushes.Relay: uses contacts and an armature; not typically a sliding plunger inside a tubular coil.

Common Pitfalls:
Assuming every coil-actuated device is a solenoid; relays are optimized for switching contacts, whereas solenoids generate linear force and stroke.

Final Answer:
A solenoid