FAA AMT (Aviation Maintenance Technician) Airframe Practice Exam

The direction of rotation in a DC electric motor is determined by the polarity of the magnetic fields in the field and armature windings. By reversing the electrical connections to either the field or armature windings, the polarity is also reversed, resulting in a change in the direction of rotation. Option A is incorrect because cooling the motor does not affect the polarity of the magnetic fields. Option B is incorrect because reversing the electrical connections to the motor housing would only reverse the direction of rotation if the motor was a reversible design. Option D is incorrect because increasing the voltage supplied to the motor may result in a faster rotation speed, but it will not change the direction of rotation.