In a DC motor, why does the coil stop rotating after 90° if current direction is not reversed? Which mechanical feature solves this issue?
DC موٹر میں رو کی سمت نہ الٹی جائے تو کوائل90° کے بعد کیوں رکتی ہے؟ کون سا میکانی جزو مسئلہ حل کرتا ہے؟
Solution & explanation
Torque falls to zero at alignment and reverses sign after it, tending to return the coil. Inertia may carry it past alignment, so “stops exactly at 90°” is an idealisation. The split-ring commutator reverses current each half-turn, keeping useful torque in one sense.
Independent study answer. Original textbook ↗ · English-medium printed page 137.