Red Seal Electrician Practice
Wiring and componentsQuestion 12 of 1506

Why do electromechanical contactors still dominate very high current switching?

  1. Solid-state relays cannot be turned off once they have been turned on
  2. Solid-state relays are too expensive at very high current ratings
  3. Solid-state relays need a 480 V AC control input
  4. Solid-state relays spark badly when they open
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Correct answer: Solid-state relays are too expensive at very high current ratings

Cost limits solid-state relays at high current.

Source: Lessons in Electric Circuits IV: Digital (Kuphaldt), 5.5: Solid-state Relays

Practice wiring and components

Questions last reviewed: 18 October 2026