🔍 Key Concepts

• DC motor rotation and torque depend on the interaction between the armature current and the magnetic field • Reversing either the armature current direction or the field polarity will reverse the torque direction • Some changes to brushes or interpoles affect commutation quality, not rotation direction

💭 Think About

• Which part(s) of a DC motor determine the direction of the developed torque: the brushes, the main field, the armature current, or the interpoles? • If you reverse the polarity of both the armature and the field at the same time, what happens to the direction of rotation—does it change or stay the same? • Which of the listed actions would actually reverse the relative direction between armature current and main field, rather than just improving commutation or reducing sparking?

✅ Before You Answer

• Identify which choice directly changes the main field polarity seen by the armature without changing both field and armature together • Confirm which components (brush position, brush order, interpoles) are mainly for commutation/sparking control, not for setting rotation direction • Recall that to reverse rotation, you must reverse only one: either the armature current direction or the main field polarity, but not both simultaneously