Maintenance Technician 2025 Complete Practice Test

The use of a shading ring in AC solenoids plays a crucial role in mitigating the humming noise often associated with their operation. When an AC current flows through the solenoid coil, it creates an alternating magnetic field that can cause the armature to vibrate, leading to the unwanted humming sound. The shading ring, typically a small piece of conductive material placed around the solenoid's pole, effectively alters the magnetic field distribution within the solenoid.

By creating a secondary magnetic field and phase shift, the shading ring helps to reduce the intensity of the vibrations. This results in less movement of the armature, thus minimizing noise levels and allowing for quieter operation. The design of the shading ring allows it to induce a small current when exposed to the magnetic field, which further aids in providing smoother operation of the solenoid.

Using a spring return or thicker coil may address other performance issues of solenoids but does not specifically target the reduction of humming caused by magnetic fluctuations. Additionally, AC solenoids do exist; hence the notion that there are no AC solenoids is incorrect in this context.