Red Seal Electrician Practice
Motor controlsQuestion 110 of 1506

In a permissive string, a high fuel pressure switch uses a normally closed contact. Why?

  1. It must close when pressure rises, so the string stays complete
  2. Normally open contacts cannot carry the fuel signals through the string
  3. It must open when pressure rises, as its normal state is low pressure
  4. It must be wired in parallel with the others to give a start
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Correct answer: It must open when pressure rises, as its normal state is low pressure

Normal state is with no pressure applied.

Source: Lessons in Electric Circuits IV: Digital (Kuphaldt), 6.3: Permissive and Interlock Circuits

Practice motor controls

Questions last reviewed: 18 October 2026