🔍 Key Concepts

• DC motor basics – relationship between field polarity, armature current, and direction of rotation • Right‑hand rule / motor rule – how magnetic field and current direction determine torque direction • What happens when both the field polarity and armature (brush) current direction are changed at the same time

💭 Think About

• First, imagine what happens if you reverse only the armature current with the field kept the same. What does that usually do to the direction of rotation? • Next, imagine what happens if you reverse only the field polarity and keep the armature current the same. How does that affect the torque direction? • Now combine both changes: if you reverse both field polarity and armature current together, how does the torque (and therefore rotation) compare with the original case?

✅ Before You Answer

• Be clear on how torque direction in a DC motor depends on both magnetic field direction and current direction in the armature conductors • Distinguish between effects that would prevent starting (e.g., no field vs. reversed field) and effects that would cause overheating (e.g., shorted turns), and see if either really applies here • Verify whether making two equal and opposite changes (field and armature) cancels, doubles, or otherwise alters the net torque direction on the armature