Red Seal Electrician Practice
Wiring and componentsQuestion 62 of 1506

A conductive-liquid level control uses two probes in a tank. Why should the full load current not be switched through the liquid?

  1. It is dangerous, so a relay on a small current is used
  2. The liquid would stop conducting once the current gets high enough
  3. The probes would act as a transformer and induce a voltage in the tank wall
  4. The relay coil would lose its magnetism when the liquid touched it
Show answer

Correct answer: It is dangerous, so a relay on a small current is used

A special relay uses a tiny current through the liquid to switch the real load.

Source: Lessons in Electric Circuits IV: Digital (Kuphaldt), 4.1: Switch Types

Practice wiring and components

Questions last reviewed: 18 October 2026