Increasing the armature spring force or magnet gap in a relay results in higher pull-in voltage or current values and higher drop-out values. Choose the correct action that causes this change.

• A. Decreasing
• B. Increasing
• C. Increasing the coil resistance
• D. Increasing the contact area

Answer: (B)

When a relay moves, it must overcome opposing forces on the armature—the spring pushing it back and any air-gap reluctance from the magnet gap. If you increase the armature spring force or widen the magnet gap, the coil must produce more magnetic pull to overcome those opposing forces. That raises the current or voltage needed to pull in (pull-in) and also raises the current/voltage at which the armature releases (drop-out) because the magnetic force must still exceed the stronger opposing force to hold or release the contact. So the action that causes this change is increasing the opposing forces. Decreasing them would lower the thresholds, and the other options don’t directly cause higher pull-in or drop-out values.