Trent builds a model electric motor. When he connects a battery to the motor, the motor spins through a half rotation and stops.

A DC motor’s commutator reverses the current in the armature every half turn so the motor keeps spinning in the same direction. If the motor turns half a rotation and then stops, the commutator may not be reversing the current. Checking the commutator is therefore the best choice.

AI-written and checked against the verified answer.