Low voltage motors can be bought from suppliers either mounted on a plastic or wooden board. The main advantage of mounted motors is that they usually incorporate 4mm sockets so that pupils can connect them to a circuit using standard lab leads without having to struggle with crocodile clips etc.
The motors are usually rated at about 3-6V D.C and as such a label should be attached to warn pupils about exceeding this voltage. Pupils will however sometimes ignore these warnings and connect to a higher voltage or an A.C current usually resulting in a burn-out of the motor contacts. The motors can be purchased separately very cheaply singly or in packs of ten or more. They can be used to replace broken motors by soldering a new one in place. The motors will happily run in both directions so it does not matter which way around you connect them.
A simple alternative to the mounted motor would be to attach flying leads and 4mm plugs to individual motors. A length or mains (two core) lead can be soldered directly to the motor terminals providing a strong (yet unfortunately not unbreakable) anchor for the leads. Shrink sleeving can be used around the soldered end to create a more secure attachment.
An electric motor converts electricity into mechanical motion. The reverse task (converting mechanical motion to electricity) is done using a dynamo. In many cases, motors and dynamos only differ in their application and are essentially the same piece of equipment.