🔍 Key Concepts

• Basic operation of a DC motor – how torque is produced from interaction of field and armature currents • Difference between DC and AC motor control (phase sequence applies to AC) • What part of a DC motor you must change so that the magnetic forces act in the opposite direction

💭 Think About

• Ask yourself: In a DC motor, if I want the shaft to spin the other way, which magnetic field (armature or field) do I need to reverse? • Consider which choices clearly apply to AC motors or power electronics rather than to a simple DC propulsion motor. • Think about how changing only the strength of the field (weak/strong) differs from actually reversing the direction of rotation.

✅ Before You Answer

• Verify which option actually reverses current direction in a winding (not just its magnitude). • Eliminate any choice that clearly refers to AC phase sequence, which is not how a DC motor is reversed. • Check which option is commonly used in practice on ships for reversing DC propulsion motors via contactors or switching of field leads.