Which statement correctly describes a solenoid?

A solenoid is an electromechanical device that converts electrical energy into linear motion through electromagnetic principles. When electric current passes through the coil of wire in the solenoid, it creates a magnetic field that moves a metal plunger or rod, thereby producing motion. This functionality is at the core of what defines a solenoid, distinguishing it from purely mechanical devices or those powered by pneumatic or battery sources.

The characteristic of being controlled electromagnetically is key to understanding a solenoid's operation and applications. It is widely used in various devices, including locks, valves, and actuators, where controlled movement is necessary.

In contrast, the other options describe characteristics that do not fit the definition and operation of a solenoid. A purely mechanical device lacks the electromagnetic component that makes a solenoid work. While a solenoid can indeed be powered by a battery, it is not limited to that power source; it can also function with alternating current or direct current from other electrical supplies. Pneumatic power pertains to devices that operate using compressed air, which does not apply to how a solenoid functions.