Final answer:
Mica is used for insulation between the bars on the commutator of an electric motor because of its superior insulating properties and ability to handle high temperatures.
Step-by-step explanation:
The material used for insulation between the bars on the commutator of an electric motor is often mica. Mica is a naturally occurring mineral with excellent electrical insulating properties and can withstand high temperatures which is essential for the functioning of motors. The commutator's function is to reverse the direction of current in the armature windings, and this requires robust insulation to prevent short circuits and ensure efficient operation.