A model electric motor that works

Purpose

Visualising difficult concepts in 3-D is always challenging, especially for pupils that have a limited experience of the world around them. By using this simple working model of a motor, pupils were able to see the key parts involved and apply their basic knowledge of Fleming's left hand rule to the complicated 3-D situation found for a motor. More than addressing specific misconceptions, the simple motor allows pupils that find visualising 3-D problems the chance to see the problem in front of them.

Benefits

Fleming's left hand rule and its application to the motor effect can be conceptually challenging topic to grasp for AS level students. The ability to build a simple motor greatly improves a pupils understanding of the physics involved. There are many commercial kits available that allow pupils to construct a motor however most of these are cumbersome to make and also quite costly.

The activity

Using a paper cup, 1 m of insulated copper wire, 2 paper clips and 2 neodymium magnets a simple motor was demonstrated using a battery.

The photographs show clearly how the motor can be constructed.

A split ring commutator was produced by removing the insulation from the end of the copper wires and marking the exposed ends of the copper wire with two black marker strips.

Investigations

For investigation purposes, pupils were able to see the effects of varying:

(1) the length of wire in the coil
(2) the magnetic field strength (by moving the coil away from the magnet)
(3) the current required to make the coil turn.

Extension

The idea for a simple motor that pupils could construct was seen at the ASE conference 2007 and as well as being cheap to construct had the added benefit of being able to demonstrate Fleming's left hand rule with respect to a speaker as well.

By using either a signal generator attached to the coil or the output of an mp3 player, pupils can make a primitive loudspeaker with the same apparatus.

Last updated: 31 May 2007