Motor controlsQuestion 236 of 1506

How does a paddle-wheel level switch tell that a grain bin is full to its height?

  1. The grain heats a bimetal strip in the bin
  2. The grain bridges two probes in the liquid
  3. The grain blocks a beam of radiation in the bin
  4. The grain stops the paddle turning
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Correct answer: The grain stops the paddle turning

A small motor turns the paddle. When material reaches it, the paddle cannot turn.

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

Practice motor controls

Questions last reviewed: 18 October 2026