Question

which would ultimately cause the armature in an electric motor to spin?
the current in the armature stops.
the gap in the commutator closes.
the current in the armature is reversed.
the commutator loses contact with the brushes.

Explanation:

To determine what causes the armature in an electric motor to spin, we analyze each option:

• "The current in the armature stops": If current stops, there's no magnetic force to cause rotation, so this is incorrect.
• "The gap in the commutator closes": Commutators have gaps to reverse current; closing the gap would disrupt the mechanism, not cause spinning, so incorrect.
• "The current in the armature is reversed": In an electric motor, the commutator reverses the current in the armature coils. This reversal changes the direction of the magnetic force on the armature, allowing it to continue spinning (otherwise, the armature would stop when the magnetic forces align). So this is the correct cause.
• "The commutator loses contact with the brushes": If contact is lost, current can't flow, so no rotation occurs, incorrect.

Answer:

The current in the armature is reversed.