🔍 Key Concepts

• Relationship between field coil polarity and magnetic poles on a synchronous motor rotor • What it means physically when adjacent poles are the same polarity versus opposite polarity • How the steel bolts’ attraction or repulsion indicates the magnetic condition of the two adjacent poles

💭 Think About

• Look at coils 3 and 4 in the illustration: if the steel bolts on these two poles repel each other, what must be true about the magnetic polarity of those two poles? • On a properly wound ten‑pole synchronous motor, what should the polarity sequence be as you go around the rotor from pole 1 to pole 10? (Think N, S, N, S, …) • If only one coil were reversed versus both being correct, how would that affect the polarity pattern around the rotor and what would the bolts on poles 3 and 4 do?

✅ Before You Answer

• Verify that adjacent poles in a healthy rotor must be opposite polarity (N next to S). • Check whether repulsion of the steel bolts means the two poles are like poles or unlike poles. • Trace the N/S pattern all the way around the rotor for each answer choice and see which pattern matches the observed repulsion between poles 3 and 4.