Red Seal Electrician Practice
MotorsQuestion 1240 of 1506

What do the Hall effect sensors do in a small brushless DC motor?

  1. They measure the stator temperature during operation.
  2. They sense the rotor position so the phases can be switched in time.
  3. They limit the current while the rotor is starting.
  4. They filter the supply voltage before it reaches the stator coils.
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Correct answer: They sense the rotor position so the phases can be switched in time.

The sensor sees the passing rotor pole and sets the timing of the stator current.

Source: Lessons in Electric Circuits II: AC (Kuphaldt), 13.6: Brushless DC Motor

Practice motors

Questions last reviewed: 18 October 2026