A solenoid is a long coil of wire wound in the form of a helix. When an electric current flows through the wire, it generates a magnetic field along the axis of the coil. The magnetic field produced by a solenoid is similar to that of a bar magnet, with one end behaving like a north pole and the other like a south pole. Solenoids find wide applications as electromagnets in devices such as electric locks, relays, and transformers. Their ability to produce a strong and controlled magnetic field makes them essential components in various technological and industrial applications.