🔍 Key Concepts

• Wound-rotor vs squirrel-cage induction motors and where the rotor circuit is accessible • How speed control is commonly achieved in different types of AC motors • Which motor types have slip rings that allow external resistances (like a rheostat) to be connected to the rotor

💭 Think About

• First, ask yourself: which of these motor types has a rotor that you can actually connect external resistors to? • Think about how synchronous motors operate: does their speed vary with rotor resistance, or is it locked to supply frequency? • Between the two induction motors listed, which one has a rotor construction that allows adding resistance in the rotor circuit for speed control?

✅ Before You Answer

• Identify which motors have slip rings and brushes on the rotor, allowing a rheostat to be connected. • Confirm which motor’s speed can be varied by changing rotor circuit resistance, not just supply frequency or voltage. • Eliminate any motor types whose rotor is short‑circuited internally and not accessible from the outside.