Red Seal Electrician Practice
Wiring and componentsQuestion 1 of 1506

A mechanical switch closes and its contacts rebound for a few milliseconds before they settle. What causes this?

  1. Arcing that welds the two contacts together until the current is removed
  2. Heat that expands the contacts and pushes them apart
  3. The mass of the moving contact and the springiness of the mechanism
  4. Residual magnetism that holds the contacts open briefly
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Correct answer: The mass of the moving contact and the springiness of the mechanism

The moving contact has mass and the parts are elastic, so the contact rebounds on closing.

Source: Lessons in Electric Circuits IV: Digital (Kuphaldt), 4.4: Contact “Bounce”

Practice wiring and components

Questions last reviewed: 18 October 2026