Red Seal Electrician Practice
Wiring and componentsQuestion 11 of 1506

A solid-state SCR or TRIAC relay turns off its AC load only when the load current falls below the holding current. What is the benefit?

  1. No inductive voltage spike, since the current is not cut at a peak
  2. The relay can switch very high currents at a lower cost than any contactor can
  3. The relay needs no input signal to hold the load on once it is switched
  4. The relay keeps the load energized for a short time if the supply fails
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Correct answer: No inductive voltage spike, since the current is not cut at a peak

This is called zero-crossover switching. Cutting a current peak in an inductive circuit would make large voltage spikes.

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

Practice wiring and components

Questions last reviewed: 18 October 2026