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. What action is described?

• A. Decreasing
• B. Increasing
• C. Reversing polarity
• D. Oscillating

Answer: (B)

Increasing the pull required to move the armature is the action described. In a relay, the armature is drawn in when the magnetic force generated by the energized coil overcomes opposing forces from the armature spring and any existing air gap. If you strengthen the armature spring or widen the magnet gap, you raise the opposing force or reduce the magnetic coupling for a given current. That means you must raise the coil current (or voltage) to reach pull-in, and you must maintain even more magnetic force to stay engaged, raising the drop-out threshold as well. So both pull-in and drop-out values go higher when you increase the spring force or the gap.