🔍 Key Concepts

• DC propulsion motor basic theory – how field windings and armature work together to set rotation • Effect of reversing current in only the armature vs only the field vs both at the same time • Relationship between direction of magnetic field and direction of armature current in determining rotation

💭 Think About

• Think about what determines the direction of torque in a DC motor: is it the direction of current in just one part, or the interaction between two magnetic fields? • Consider three cases separately in your mind: reverse ONLY the armature, reverse ONLY the field, and then reverse BOTH. In which cases would rotation reverse? • For each answer choice, picture what physically happens inside the motor (magnetic field, force on conductors, brush/commutator behavior). Which options describe a real, expected effect, and which sound unlikely or extreme for this simple change?

✅ Before You Answer

• Recall the right‑hand rule or motor rule: torque direction depends on both field direction and armature current direction. • Verify which changes would realistically cause overheating of brushes versus simply changing electrical polarity. • Ask yourself: if both the field and armature polarities are flipped together, does their relative orientation change or stay the same?