Which indicates a properly operating relay when energized?

• A. It Clicks
• B. It Hums
• C. It Glows
• D. It Vibrates

Answer: (A)

When a relay is energized, the magnetic field pulls the armature so the internal contacts snap from one position to the other. that rapid movement is typically heard as a clear click, and it confirms the coil is attracting the armature strongly enough to overcome the spring force and reliably change the contact state. That audible click is the most reliable sign the relay is functioning as intended.

Humming means the coil is energizing but the armature isn’t moving cleanly or fully, which can indicate marginal current, coil or core issues, or mechanical binding. Glowing isn’t a normal behavior of the relay itself and would usually point to an indicator component or a leak path rather than proper relay action. Vibrating suggests the mechanism isn’t settling properly—this can come from mounting, resonance, or insufficient damping, and it’s not a sign of healthy, steady operation.

So, the crisp click on energization is the best, most direct indicator that the relay is operating correctly.